Build This Simple "Low Distortion" Signal Generator For Your Projects
Added 2017-06-01 20:30:33 +0000 UTCBuild a signal generator with better distortion specs than most on the market! It requires very few parts and is a great learning tool. Learn the Math, and some neat short cuts that will make you a pro in no time. See the attachments below for a Schematic and the Math "simplified." Follow along with your calculator, and you'll learn this in a snap.
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Comments
I have question about making this variable. What would the maximum range be for frequency of this setup with double variable resistors adjustment and capacitor selection switch?
John E Barron III
2025-05-14 13:47:38 +0000 UTCWow funny how the math works out for the equation 1 over 2pi. You stated that Pi is 3.14 and that 1 divided by 2Pi = .159 did you know that Pi taken to 5 decimal places is 3.14159?
John E Barron III
2025-05-14 12:58:44 +0000 UTCgreat thinking I think thats just just the kind of thinking Mr. Carlson is trying to teach everyone to do in this course. Experiment and see what works to help develop your skills and mindset. So thanks for sharing your thoughts because it will help me and hopefully others. Im a relatively newbie so I'm trying to soak up as much as I can from Mr. C and all of our very knowledgeable members.
Wailin Free
2023-11-15 03:14:55 +0000 UTCHi Andre
Wailin Free
2023-11-15 03:09:22 +0000 UTCCouldn't you decrease the distortion even more by adding a few RC filter networks at the output and then anohter OpAmp?
Andre
2023-06-04 17:06:06 +0000 UTCI’m interested in building this and potentially using it to calibrate tape machines, for that I need a 1KHZ sine wave -10 DBV… I wonder if I’d be able to get this thing to work for those purposes, if anyone has built this project, please let me know your thoughts! Thank you.
Ben Lindvall
2023-04-19 17:26:43 +0000 UTCGreat Work
LoSaYa
2022-10-11 23:14:22 +0000 UTCI found the bulbs on mouser, 10 for under $15. Amazon wanted $75 for 10 I believe. You have to be very careful, halogen and led versions are much more common. Many of these projects have items that were easily available when the video was produced, not always true 4 or 5 years later.
Timothy M Tapio
2022-01-22 19:49:05 +0000 UTCI used 1819 bulbs (on hand and cheap). The gain would fluctuate over a period of a second or two - looked like it was breathing! The bulb evidently has far too much thermal inertia for 1KHz. Using 47nF caps put the frequecy over 2k, but it is solid as a rock. for curve-tracing duty, 2K is fine. I didn't have any trouble powering the thing - 6mA on each of + and - 15V. Looking around, I see 8 power supplies in my shop!
Dan Barker
2021-12-30 21:26:03 +0000 UTCMaking sure the capacitors are poly type is critical for success in achieving a stable waveform in oscillator circuits as my own experience can attest. I initially breadboarded this circuit using parts on hand, which included the TL072BCP variant of the op-amp. As I did not have the right value poly style caps, I had also substituted ceramic caps for the poly style. After power-up and the lamp settling down, this usually resulted in a nice stable waveform for a few moments, but then it would become completely unstable with lots of jitter and some associated frequency drift. Sometimes it never did stabalize after power-up. Adjusting either of the two potentiometers would also introduce lots of jitter. Additionally, it was almost impossible to achieve the recommended 2 volts peak-to-peak value at Pin 1 of the IC. My initial thought was that I may have had a bad or counterfeit op-amp as experienced by another user here. I made a special purchase of TL072CP TI brand chips at Digi-Key, but I ended up with exactly the same results. Then I realized that the root cause was most likely the type of capacitors I was using, and I obtained some metalized mylar polyester film capacitors. The difference was phenomenal, with a completely stable waveform that stays that way for hours. Adjusting the pots now also became very easy, with no associated jitter. The frequency drift totally disappeared and setting the 2 volt peak-to-peak value at Pin 1 was very easily achieved; again this value no longer drifted. Some design notes: I used a 1% precision resistor for the RC connection between Pins 1 and 3, acheiving a measured value of 1581 ohms. A 10-turn precision 2K pot was used between Pin 3 and ground for the frequency adjustment, and a 10-turn precision 500 ohm pot was used for the voltage adjustment between Pins 1 and 2. This achieved a very accurate and stable result allowing me to set the frequency to 1.004 Khz with precicesly 2.0 volts peak-to-peak as seen on the scope, and no drift of either value after several hours. A BNC connector is routed through a DPST switch to Pin 1; the other side of this switch is connected to the output of Pin 7, allowing selection of either a fixed low-voltage source or as an amplified source. I'm easily acheiving 20 volts peak-to-peak output without clipping.
John Moorhead
2021-12-02 11:08:25 +0000 UTCImagine them with transatlantic delivery cost! Just use what you got at hand, as advised by Mr. C in the video. You may need to adjust the trimpot value - need to cover 2x bulb resistance.
Piotr Korczyk
2021-11-22 06:07:17 +0000 UTCI just ordered a dozen bulbs for about $1.25 each. Also have TL072CP's coming from Newark. I have not ordered from Newark in decades.
Mark Shaum
2021-10-05 23:49:14 +0000 UTCDual will probably work - up to a point but the key to this circuit is the bulb. It's a heat sensitive resistor which is what creates the sine wave in effect by dint of it cooling and heating as current flows and its impedance changing as it does. That's why the voltage (which determines the current of course) is so crucial to this circuit. Paul Falstad has a circuit simulator that I find handy for pre-prototyping work. There's nothing like Mr. C and a real breadboard but it's more comfy when you're sat in bed!
Marc Draco
2021-08-28 00:19:47 +0000 UTCHoly cow batman! Those bulbs are pricey now!
Marc Draco
2021-08-28 00:06:12 +0000 UTCAny reason we cannot build this on a 9v battery power supply?
jake loewenheim
2021-05-19 06:01:21 +0000 UTCOk, so I decided to build this, I do not have the exact parts yet but I started prototyping already with some parts I do have, what I have noticed is that no matter what bulb I use, unless I give it enough gain to just touch the dc rail limit/barely noticeable clipping, the wave has a slight periodic bounce to it/oscillation....with a fixed resistor instead of a bulb the wave flatlines completely if it does not touch the dc limit...very interesting and any explanation would be most appreciated, below is a link with my test set up for your viewing pleasure :) https://streamable.com/4c8cl8
Andu
2021-03-25 16:21:29 +0000 UTCHi, I've managed to get my oscillator working using the cm7387 lamp(man they were expensive but i managed to get 10 for £23.00 in the end from the US) and the TL072 op amp, ive used some PCB strip-board to build a board i am going to fit into a Hammond plastic project box, here's a picture https://ibb.co/KDLhF2x the sine wave output i get can be seen in the next two pictures. if you look at the sope screen you can see the DC voltage tracking the sine wave, i used the peak detector circuit Mr C gave us on the breadboard to give me my DC peak voltage https://ibb.co/XW6w7gh https://ibb.co/v3rJwBp i made my own -15/+15 volt power supply (it can produce 1.5 amps so is way overpowered for the oscillator but i can use it to power more than just this oscillator at the same time) It uses a 230V Pri to 2x 18V sec transformer, two 40V B40R bridge rectifiers , an LM7815, LM7915 and two 35V 1500uF rubicon filter capacitors. here's a picture. https://ibb.co/6NJTPjg
David Marchesi
2021-03-24 12:47:15 +0000 UTCThanks, I was looking for just this board.
Fred Winograd
2021-03-21 21:09:25 +0000 UTCNevermind! Turns out I had fake/counterfeit TL072 OpAmps. After a re-order everything is working great. Anyone feel this might be happening to them, this page was a huge help, https://forum.allaboutcircuits.com/threads/wien-bridge-oscillator-op-amp-lamp-stabilized-crossover-distortion-with-tl072-not-ne5532.158474/
Raymond Van Valkenburg
2021-02-10 14:48:20 +0000 UTCHello, I've noticed a few others posted about having unstable voltages while setting the R1 resistance but with no reply. I am having the same problem. I can't get Pk-Pk even close to 2V. Anything below 5V and it goes all over the place wildly. Any advice? Just touching my potentiometer (R1) makes the voltage/amplitude go nuts. To add, it's holding at 1.008Hz just fine.
Raymond Van Valkenburg
2021-02-02 19:42:04 +0000 UTCHi, I'm new here, I don't know if you received an answer but I had the same problem at first. I found that I had to much amplitude on the 250k -500k vr. If you dial it down it should turn it into a sine wave, or at least it did with mine. Also I used 1% metal resistors, they are common in audio circuits. Also I tried a variety of mkt style caps and green caps it made no difference on the scope. Hope this helps.
David Ryder
2021-01-18 08:54:37 +0000 UTCAnother power supply that is convenient and cheap is this one. https://www.mouser.com/ProductDetail/MEAN-WELL/DLW05A-15/?qs=%2Fha2pyFadugLPkTIbXLHPmIcBsaCziduAXh%252BaHvwPOg%3D
jeffrey wagner
2021-01-03 05:07:31 +0000 UTCMr. Carlson, how important is the use of Carbon Composition resistors and Poly-style Capacitors in this circuit? I have made it with the components that I have and got a square wave, not a sine wave. Is that because the capacitors and resistors are not closely matched like you have shown in the video? Thanks.
cyb3rfly3r
2020-12-30 06:26:43 +0000 UTCThat distortion analyzer is one of the most impressive things I have ever seen. Do you mind letting us know what that is? I don't recognize it.
Leonard Peters
2020-11-29 19:05:59 +0000 UTCHere is the power supply on Amazon. DROK Mini Boost Voltage Converter DC 3.2-13V to DC ±15V Positive Negative Dual Output Power Regulator Module 100mA Step Up Volts Transformer Board
Kenneth Graham
2020-11-23 22:22:38 +0000 UTCAnyone looking for a cheap 15v dual rail power supply, there is one on Amazon that works great for this signal generator. Among other things. It's great because it can be powered by anything form 3v, up to 13vdc. Close to that, can't remember exactly. There are higher power ones also.
Kenneth Graham
2020-11-23 22:21:39 +0000 UTCWe need to build a THD distortion analyser. I think that would be a great project. As for the signal generator, I had a couple OPA2134 ultra low distortion op amps I decided to try. Even without the 2nd gain stage, I'm getting 20vpp plus. R1 will only get it down to 10vpp or so before it starts to oscillate. I think the gain is about the same as the tl072. Haven't figured out why yet.
Kenneth Graham
2020-10-29 14:07:06 +0000 UTCPi is intimately locked into the formula for angular frequency and 2 pi is a complete circle in radians. In the mechanical world, 2 pi is multiplied by a function of mass and spring constant to give frequency. I'm new to the electronic world, but the formula given is very familiar to me, I see the formation of a circle (ergo a sine wave) and something taking the place of a spring and body. Sorry I can't give you a solid answer though.
Sibilator
2020-09-23 00:04:07 +0000 UTCThis is great! I'm very curious as to where pi comes into the equation. I did not get that from the first watch of the video.
Robin
2020-09-10 08:08:44 +0000 UTCI get 2v and 20v initially but after a couple of seconds the readings start pulsing wildly and cant see why. Any ideas appreciated. Thanks
SAJ507
2020-07-18 06:36:09 +0000 UTCActually a PCB version seems to need the 7380 Bulb to run, 7387 version did not run at all ( it had to much resistance). I guess one of those things that change from breadboard to PCB.
Vincent
2020-07-03 02:23:27 +0000 UTChttps://drive.google.com/file/d/1bsegTvJqSnbykt2HgpXRdoWB_8Icsp9w/view?usp=sharing
Steve Edwards
2020-06-30 19:53:08 +0000 UTChttps://drive.google.com/file/d/11CkO7afzx5pO_Wiy5MreB3vZEfiy1rKL/view?usp=sharing
Steve Edwards
2020-06-30 19:52:27 +0000 UTCI got a 1kHz sig using an LM358N op amp and an unknown (assume 12V) bulb type of 36 ohms DC which gave a nice 20Vpp output - not using the other amp pairs yet! You can see pics on my site at:
Steve Edwards
2020-06-26 22:05:08 +0000 UTCHi Paul
Steve Edwards
2020-06-26 22:02:42 +0000 UTCThe fun goes on with changing the bulbs. The 7380 bulb which is used in the later curve tracer gives a much different wave form.The initial resistance of the filament has something to do with it. I got almost a square wave with an old mag light (low resistance bulb). The 7387 which has a moderate resistance gives a nice sine shape. I night light filament got to resistive and I got nothing at all. I guess the curve tracer works better with a flatter curve since Mr. Carlson changed the bulb to an 7380 it in the later design. A 40W Mini-Reflector bulb from Phillips gives the same result as the 7380, if anyone needs an obscure substitute ;)
Vincent
2020-06-10 02:26:57 +0000 UTCGot it to run at 1kHz. Nice project and lots of learning. Thanks Mr. Carlson
Vincent
2020-06-09 00:45:50 +0000 UTCSimplifying the 1 over 2Pi constant into 0.159 is a great idea. Instead of multiplying R and C together before the division, I divide R an C separately, sometimes. It works great when you know the capacitance and want to figure what value of R will give you the frequency you seek. In the example, dividing .159 by .0000001 F equals 1,590,000. It's easy to visualize what values will get you in the ballpark. Dividing 1,590,00 by 2.5K gives 636 Hz. And, it's intuitively obvious, that dividing by 1.59K will yield 1,000 Hz.
Steven Ruhl
2020-06-03 15:58:58 +0000 UTCUS$0.72 for a bulb....with US$61.00 postage to Australia. Won't be building this project anytime soon, unfortunately!
SAJ507
2020-06-03 09:35:40 +0000 UTCVery enjoyable! Actually building it is a very different experience to reading about it in a book. I am in the UK; I found this bulb worked for me (with +/-10V supply) https://cpc.farnell.com/omron-industrial-automation/a16-24/lamp-bi-pin-28v/dp/SW04539 which they sell in singles.
Tristan Williams
2020-04-04 16:52:35 +0000 UTCAm I okay to use a tle2426 for the central ground on this? dual supplies are a faff. EDIT: Yep, virtual ground is fine. also as I am still waiting on TL072's I used http://www.ti.com/lit/ds/symlink/tl081.pdf tl081's (mind the pin changes) EDIT AGAIN 072's arrived. Solid.
Twobob
2020-02-29 23:40:23 +0000 UTCAs a musician I salute you, EDIT#: Yup this was immense fun, had everything from hard bass down at 300 Ohms, through to crumbling upper harmonic saturation and fading fundamental when starving the Volts and riding the feedback hard in the upper K's range. Just a few of these muxxed, mixed, chained, whatevered could give some incredible AM's :) Super fun. My bulb worked great. I think I list the part in Community. Super stable but with just enough wobble to be interesting, really low distortion looking at the spec, probably just more noise than yours, Paul.
Twobob
2020-02-05 21:53:23 +0000 UTChttps://drive.google.com/file/d/1LskPkobLbwHeLDdI4tvqbX56Y_0LQg7i/view?usp=drivesdk It worked! I'm using a TL084 at the moment but I'm waiting for a batch of TL072.
Gianluca Tovo
2020-01-28 23:30:39 +0000 UTCMUCH MUCH APPRECIATE all you do! Clear, concise and to the point. Great stuff!
Mike Tutt
2019-12-29 18:33:22 +0000 UTCYour phone will have "much higher" distortion than this signal gen. You can use your phone as a signal generator when distortion is not an issue (like signal tracing.) Low distortion signal generators are use for measurement and calibration.
Mr Carlson's Lab
2019-12-29 17:08:51 +0000 UTCCan someone provide some insight on the following.... I’m guessing this low distortion signal generator has some much better specs than the free APP I downloaded on my ipad called f Generator made by EE-toolkit.com. The app produces several different waveforms from 20-20kHz. I think I remember the high output around 220mv....but not sure. 1. What’s the difference in tracing a signal thru a circuit with the ipad app sig gen versus the low distortion sig gen we're building here? Thanks
Mike Tutt
2019-12-28 03:39:17 +0000 UTCThanks for your input Johan!
Mr Carlson's Lab
2019-11-26 21:44:45 +0000 UTCAnother good video and useful project. Do you perhaps plan a "valve tester" project, that will be really nice. ;)
Johan De Vries
2019-11-25 11:44:13 +0000 UTCThe oscillator output is set to 2.2 V peak to peak. 10 X gain gives you 22 V p to p or -11 Volts to + 11 Volts. That is well within the +/- 15 Volt supply and the capability of the TL072.
Joseph P. Miller
2019-10-31 19:24:24 +0000 UTCBecause my spectrum analyser starts at 9khz ,If I ran this oscillator at 10khz instead of the 1khz to check the THD ,would that be a good representation of it running at 1khz or would the harmonic distortion alter to much
Garry Norbury
2019-10-13 08:41:53 +0000 UTCHi Garry. It's a Stanford Research SR780
Mr Carlson's Lab
2019-10-01 22:42:43 +0000 UTCWhat was the make of your Spectrum Analyser
Garry Norbury
2019-10-01 08:13:58 +0000 UTCSo I think I'm missing a key concept here, if I have a 15 volt split rail powering my op amp, won't that limit my peak to peak voltage at the output of the final? I can increase my positive and negative rails to 22 v respectively on each and get the predicted 10x gain, but when using the 15 volts shown in the schematic I am clipping at about 14 v Pk-Pk. This makes sense to my limited understanding. Can someone explain what I've missed?
Spec'dTrician
2019-09-01 17:55:40 +0000 UTCWhy is my 072 getting very hot when the circuit is running? There is no difference if the VR in between the op-amps is at min or at max. What is causing the dissipation? The bulb is not getting hot.
Harri Lumme
2019-08-24 14:01:36 +0000 UTCHi!
Harri Lumme
2019-08-24 13:57:57 +0000 UTCI built this one decades ago, i used a stereo VR from a car-radio to gang up the two resistors. Since my goal was to build a sine wave generator that covers the whole audio spectrum i used two capacitor pairs switched by a relay. The relay i controlled by a discretely built T-flip-flop. The overengineering was a lot of fun. I am still very fascinated by the simple automatic gain control using the light bulb.
Matthias Martin
2019-07-21 21:59:18 +0000 UTClittle awkward that im the only one having an issue with the 250-500 ohm pot. im not really finding anything that has much or anything similar to whats listed. Mr C not saying anything about it in the video makes you think that its as regular as any other.
Jared Hudson
2019-07-01 06:29:38 +0000 UTCHi Al. Looks good! Feel free to post this in the community section. I usually don't allow pix in the individual posts as they take up a lot of room.
Mr Carlson's Lab
2019-06-25 08:01:38 +0000 UTCWell, I was going to build this when I become a patron the first time about 2 years ago, but now that I became a patron again, I decided to build this circuit again. It is a neat little circuit. Next to make the PCB and I am thinking of building it using surface mount components instead of through the hole. (EDIT) Removed the pics. Looking at the parts I have I guess I intended to build the Curve Tracer but life sidetracked me for a bit. So I am going to build the curve tracer...
Al Anderson
2019-06-22 17:26:32 +0000 UTCInteresting that the extra "ringing" is only happening on the positive side of the sine wave. Perhaps the 55nf cap is too low? Or some effect from the light bulb you used. I'm no expert, those are just my guesses.
Cory Benjamin
2019-05-29 23:41:38 +0000 UTCHi Jerry. My understanding is that + and - 12 volts will work ok. I believe that the only side effect is that the maximum potential peak to peak output of the sine wave will be a bit lower for you.
Cory Benjamin
2019-05-29 23:34:30 +0000 UTCI'd love to have one of those breadboxes. They look handy as all get-out. :-)
Bruce Dow
2019-04-15 02:52:37 +0000 UTCHello Paul, Just wondering if there is a way to add some kind of fine tuning control to a B&K 2050 rf signal generator I know it's not the best but trying to adjust it on frequency can be a challenge..Maybe a short video in you're " spare time ". Tnx. Tom.
Tom pamula
2019-04-11 16:25:10 +0000 UTCHi Paul, I finally coughed up the funds to join your Patreon last month, well worth the money even though my good wife of 50 years complains a bit, our Social Security checks are getting smaller it seems and more places to spend the money. At any rate, I would like to build this. I have all the parts on hand but my little power supply will only give me + and - 5 volts and + and - 12 volts as well as the wonderful little + and - 3.3 volts. I am not all that familiar with using the negative voltage and only built the PS from a kit because many of my audio amp kits require the + and - 12 volts so you can get the right sounds out of the speakers. Do you think I can get this working if I use the 12 volts in lieu of the 15 volts? Perhaps there is some way to wire the 3.3 together with the 12 to get the 15? Not sure how that would work.
Jerry Ericsson
2019-03-04 00:38:58 +0000 UTCIf you use a quad Op Amp, don't let the idle sections just float! Wire them up as noninverting buffers and connect the + input to ground. In single voltage designs, connect the + to Vcc/2. Do NOT just ground both inputs! You are asking for latchup or random oscillations.
Steven J Greenfield
2019-01-23 22:22:32 +0000 UTCYou would have to make some wholesale changes to the circuit. Mostly, where RC is in parallel, put RL in series; and where RC is in series, put RL in parallel. Cored inductors tend to introduce nonlinearities due to a number of factors, including hysteresis of the core material. Also, large inductors for audio frequencies tend to become very unwieldy and the nonlinearities get worse.
Steven J Greenfield
2019-01-23 22:11:13 +0000 UTCThe light bulb is there to set the gain just right to keep the output as pure a sine wave as possible.
Steven J Greenfield
2019-01-23 22:06:59 +0000 UTCTry one of those tiny bulbs from a Christmas tree light string. The incandescents are often rated at only 1.5V each.
Steven J Greenfield
2019-01-23 22:00:40 +0000 UTCHello Mr Carlson. I'm new here. I am wanting to get back into electronics after a long while and figured I would start WAAAAAY back here at some basics and start to reteach things I have forgotten or never knew. I put together this circuit using what I had laying around. I got a strange wave form, perhaps you or others could help me understand why it looks as it does. Now for the sake of learning, and not having the components you used on hand, I improvised....knowing I would not get the same output freq. Here is what I am getting: <a href="https://flic.kr/p/23GhVTc" rel="nofollow noopener" target="_blank">https://flic.kr/p/23GhVTc</a> I only built the first stage at this point. I used 1K resistors and 55nF caps. I dont have much in terms of measuring equipment so I dont really have the means to match components very close. I just went with what I got. I dont have an adjustable resistor either, so I stacked 6 1k resistors in parallel for the "output - to - input" adjustment. Adding more to drop the output down. The light bulb I had was some old junk I had laying around, and my power supply only goes to 12V +/-. Also the Opamp was a TL081CP. Again, this is what I had laying around, and since it didnt work as expected, I thought GREAT!. Maybe I can gain some insight on how the out put was effected by certain changes. So I know I am only a $2 contributor right now...just getting my feet wet. If these little courses can bring me back up to speed, I value it like any other education and will happily donate more.
David Prellwitz
2019-01-19 17:37:08 +0000 UTCI'm thinking something along the lines of this: <a href="http://powersupply33.com/15v-1a-regulated-symmetrical-power-supply.html" rel="nofollow noopener" target="_blank">http://powersupply33.com/15v-1a-regulated-symmetrical-power-supply.html</a> to power this thing with the +\- 15V. Would building a circuit like this be suitable for powering the oscillator?
Matt Tucker
2018-11-20 16:02:38 +0000 UTCPerhaps this portion of his video answers your question? He explains why we need a positive and negative supply. That may not be your question exactly, yet if it does...happy to help.
Mark Oates
2018-09-21 05:48:51 +0000 UTCHi Paul,, Would this circuit work with a single power supply? Positive volts DC only instead of + and -.
Terence Kaye
2018-09-17 17:19:03 +0000 UTCThanks Paul. Another great lesson to use!
Robert Calk Jr.
2018-09-06 12:15:33 +0000 UTCHi Paul, can you please give me some recommendation? I need to replace that bulb as it is impossible to find out in Europe and from US it is extremely expensive.
Robert Košulič
2018-08-23 08:13:52 +0000 UTCYou're welcome Roy!
Mr Carlson's Lab
2018-07-12 08:24:08 +0000 UTCThanks sir Paul for this video, I was learned the math and short cut to calculate device to know the cycles or hz.
Escabusa Roy
2018-07-12 04:27:28 +0000 UTCThanks for your input Roman!
Mr Carlson's Lab
2018-06-22 07:41:06 +0000 UTCAlso, I am somewhat confused with all the capacitor testers you have created. I know about ESR testers, but not understanding what the purpose is for all your new designs. Regards, Roman.
Roman Charak
2018-06-22 02:33:25 +0000 UTCHello Mr. Carlson. I lashed together a dual voltage power supply on my breadboard and built the Oscillator circuit using a LT1364 Opamp (because that is what I have on hand for now). I got a beautiful 1 KHz sinewave - but the tops and bottoms of the sinewaves are doubles and jumpy on my oscilloscope screen, until I disconnect the power supply from the transformer. Then the sinewave is perfectly still, until the bulk capacitors drain off. The sinewave is perfect also when using 2 x 9 volt batteries to create a dual power supply. I suppose this has something to do with the way I have built my power supply. Maybe you could share a design for a dual power supply for us hobbyists to build? I am really enjoying all that you teach us.
Roman Charak
2018-06-22 02:31:05 +0000 UTCHi Stanley. I didn't measure the distortion of the 082, so I would use the 072. A filter may help, but any "distortion" of the sine through the filter would add to distortion. This would be something to experiment with. It would have to be a very well built filter!
Mr Carlson's Lab
2018-06-20 06:04:36 +0000 UTCI am wondering if sending the output of the oscillator through a passive low pass filter with its 3 dB cutoff frequency at 1.5 kHz and then into the output amplifier stage would further reduce the THD? Also, is the TL072 critical or would a TL082 produce the same low distortion? Thanks.
Stanley Chytla
2018-06-20 01:07:30 +0000 UTCGreat Job Toby!.... Nice scope too!
Mr Carlson's Lab
2018-04-20 03:35:51 +0000 UTCBeen looking forward to building this for a while, got it finished today. Works beautifully! Really enjoying the videos, Mr Carlson. Next I plan to use this with the transistor bias/test circuit and eventually the curve tracer. My breadboard: <a href="https://www.flickr.com/photos/qu1j0t3/27700595698/in/dateposted/" rel="nofollow noopener" target="_blank">https://www.flickr.com/photos/qu1j0t3/27700595698/in/dateposted/</a> and resulting trace <a href="https://www.flickr.com/photos/qu1j0t3/41570070211/in/photostream/" rel="nofollow noopener" target="_blank">https://www.flickr.com/photos/qu1j0t3/41570070211/in/photostream/</a> I decided to match the .1µF caps with a simple RC+555 oscillator and I believe I got within 0.25% this way after trying about half a dozen.
Toby
2018-04-20 01:04:06 +0000 UTCI think that I got this though my output is only 7x pin 1. 2.1v vs 14.3. The sine wave at pin was pretty close to 1khz. The scope output at pin 7 was a square wave which was surprising. I need to see what the next project is, though I plan to fool around with this one a bit.
George Noyb
2018-03-27 14:42:08 +0000 UTCHi Jason. Thats right, when the amplitude is to high and you can't trim it, the bulbs resistance is to low to begin with. This will give you a squared off wave. When the circuit is operating properly, you can trim the gain of the circuit (7387 bulb) and obtain a clean sine wave.
Mr Carlson's Lab
2018-03-27 07:37:22 +0000 UTCHi Paul, playing catch up on some of these projects, but this circuit is a nice learning circuit indeed! Got a square wave from a Mazda 4W 12V bulb (Is this right?) and a very stable and CLEAN sine wave from the 7387 once the springs settle down :) I'm going to build the circuit board version soon and thinking I want to do a switch between 400Hz and 1KHz for the output. Anyhow thanks as always for sharing!
Jason Doerr
2018-03-27 04:48:32 +0000 UTCWonderful to read George. Hey, you're doing great!
Mr Carlson's Lab
2018-03-23 11:51:20 +0000 UTCThen again, I started working on another project and it had a TL082CP in it so I stole it for this signal generator. Lol. I think that I have it working, my mistake at the voltage reading at pin 1 was that it needs to be measured as AC not DC, big dummy here. Anyhow, I have a very pretty sine wave on my screen and I think it is at 1k Hz . I wish there were a way to upload images here. The voltage at pin 1 reads 2.015. My2 resistors are 1.2K and they seem to be working ok. My 2 capacitors are .012 and .011, yay. Forward !
George Noyb
2018-03-22 18:49:53 +0000 UTCWell nuts. I have the wrong IC. A TL071 instead of a TL072. The pins are different so I am going to wait until the TL072 gets here. Color me a big dummy.
George Noyb
2018-03-22 16:19:12 +0000 UTCHi George, Thats a trigger level adjustment. Adjust the trigger, and you will get rid of the double image.
Mr Carlson's Lab
2018-03-20 10:04:37 +0000 UTCHi George. You want to be looking at pin 1 with a scope. The VR is a Piher PT-15 type <a href="http://www.piher-nacesa.com/pdf/14-PT15v03.pdf" rel="nofollow noopener" target="_blank">http://www.piher-nacesa.com/pdf/14-PT15v03.pdf</a>
Mr Carlson's Lab
2018-03-20 10:00:53 +0000 UTCI wired it up again because I had failed to take a voltage reading at pin 1. Turns out i cannot get below ---5.5v. How come it's negative ? Also where did you get that variable resistor ? My part store has no idea what it is. I am using a 0~500 ohm trim pot instead.
George Noyb
2018-03-19 19:52:20 +0000 UTCWell I kinda got it working but not with the parts as shown. I had 2, 1.3k resistors and the caps were close to .1uf. The math gives me a 906hz freq. so i will wait until the correct parts get here before proceding. Yesterday at a ham meet i bought 2 scopes. 1 a tektronix 465a that I havent plugged in as of yet. the other a Hameg which seems to work. I know diddly about scopes so i will need some training bbefore i can count on its measurements. Anyhow I got a sine wave but I think that it shows about 14v p to p. And although the picture shows a pretty good sine wave, it sometimes has a double image that reverts back to a single image if I touch the scope Weird. I am gonna ask a buddy if he can give me a few pointers. I am lookinh for a way to upload pictures but dont see it.
George Noyb
2018-03-19 17:32:01 +0000 UTCI seem to remember Mr Carlson saying that this circuit would go into the circuit tracer project. Would it still include the light bulb ? And it is still not clear why a simple resistor could not be substituted for the bulb. Maybe further reading will help make it clear ?
George Noyb
2018-03-02 19:28:54 +0000 UTCDear Mr Carlson, is there any way to include in this circuit an variable inductance as frequency-changing element? I am looking for signal generator with such stability as this circuit, but the variable inductance is essential for my school project (and I have it already, coil with moving ferromagnetic core, set by micrometer screw).
Michał Nowicki
2018-02-22 22:41:32 +0000 UTCI look forward to reading your results Patrick.
Mr Carlson's Lab
2018-02-19 00:02:09 +0000 UTCMy circuit is producing a sign wave at 1070 Hz with a pair of .1uF poly caps and 1.5K resistors. I tried substituting a 10 ohm resistor in place of the light bulb to see how unstable it is. The gain was very unwieldy and adjusting the trimmer was like trying to stay on a balance beam. It would look like it was fine and suddenly collapse, or go the other direction. I even tried using a 25 turn pot and it was still very unstable. Even if you just left it there not touching a thing, it was all over the place. With the 7380 bulb in place, it still very bouncy when the amplitude is changed with the trimmer and take a moment to settle down, but much more stable. I'm not sure I have a MOSFET and diodes to try some of the other topologies Jim Williams has in his notes, but it could be a very interesting comparison.
Patrick Briggs
2018-02-17 07:46:37 +0000 UTCGreat Stuff Patrick! I have this app note here as well. This is "way" overkill for this project, The distortion specs of that design are below the noise floor of my SR780, and not mentioned, would require "cherry picked" parts. A great design for those that would like to challenge their building skills.
Mr Carlson's Lab
2018-02-02 05:24:44 +0000 UTCAnalog legend Jim Williams wrote a paper on how to get THD down to an ultra low value of 0.0003% basically substituting the light bulb with a pair of diodes and a photocell. The document is at <a href="http://cds.linear.com/docs/en/application-note/an43f.pdf" rel="nofollow noopener" target="_blank">http://cds.linear.com/docs/en/application-note/an43f.pdf</a> on page 32. Really fascinating stuff.
Patrick Briggs
2018-02-02 05:09:55 +0000 UTCHi Rob. In the community page, you just have to do the load more thing. I'm glad your enjoying the oscillator circuit.
Mr Carlson's Lab
2018-01-27 12:57:21 +0000 UTC_Catching Up in Two Ways_ Mr. Carlson, taking a break from the assembly of this project, I read the Wikipedia article about the Wien bridge oscillator. I am fascinated by the history of this design and the connection to the Hewlett Packard company. Speaking for myself, the Radio Shack "100-in-one lab" kits I did as a kid were always lacking this sense of history-- who discovered this and when? What did they do before and what problem did it solve? So, in my way of thinking, this lesson brings me forward to 1939 in terms of electronics knowledge :) Second, you often refer people to the Community page, but I can't find a search capability there. Since I am several months behind the class, going back in time ("Load more, Load more") in the comments section is extremely difficult given the number of photos that have been uploaded. Is there a trick to jumping to a point in time on the community page?
Rob Clark
2018-01-26 15:21:13 +0000 UTCGreat to read Peter! Through this course, you will find that more and more, the projects you build will come to life the first time. Thanks for your kind comment as well!
Mr Carlson's Lab
2018-01-14 07:11:25 +0000 UTCI followed the instructions and got the oscillator working 1st time. Thank you Paul for such clear instructions and explanation of the theory. It really boosts your self confidence when you can get something working. The whole process of watching the lesson, getting inspired to build it, buying the parts, waiting for them to arrive, actually building the circuit and finally throwing the switch and watching the scope in anticipation. Brilliant! I'm now planning to put it into a project box. Again, thank you.
peter jeffs
2018-01-13 23:39:57 +0000 UTCHi Rodney, can you post a picture of your set up in the community section? This way I can see what's happening.
Mr Carlson's Lab
2018-01-11 12:29:48 +0000 UTCI need help. I have bread boarded the circuit .I got it to oscillate at 1.02 KHz. My problem is when I try to lower the voltage to 2 volts it stops oscillating at 4 volts. I have all the components Paul used. I am using 2 matched resistors at 1.5 K. The capacitors are somewhat close in value. I am having doubts that I am using my scope correctly. I am using a X10 probe and enabling the x10 setting on the scope. Is this correct? Thanks
Rodney Garrett
2018-01-11 06:12:44 +0000 UTCI call that "limit testing" Peter :^) I look forward to hearing your results with the proper parts.
Mr Carlson's Lab
2018-01-08 14:01:44 +0000 UTCi got this thing working with 12v+ve and 12v-ve and super touchy 1M ohm vr's! all the values are out of whack but it still works 1.3 k cycles. gonna get the right parts tomorrow and get this thing accurate.
peter
2018-01-08 13:46:57 +0000 UTCBuilt this circuit with a CA3140 BiMOS op-amp, but the output wouldn't go more than about -0.2v, almost as though half-wave rectified. Replaced it with a common LM741 and it came to life! It seems bulbs with longer filaments (hight voltage) give more bounce on turn-on than similar wattage bulbs with shorter filaments (lower voltage), which makes sense since there's more non-linear element in the circuit with the longer filament.
Klaus
2018-01-07 18:12:58 +0000 UTCAlso, apparently changing the capacitors has literally no effect on the circuit. I've tried values from 10 nano all the way up to 470 micro with no change whatsoever.
Robert Brunnemer
2017-12-18 20:48:19 +0000 UTCI am attempting to build this circuit. I have everything as it says on the schematic and am using the TL074 op amp and the 7380 bulb, but the circuit isn't oscillating at all. All I am getting is a non inverting amplifier between 5 and 12 volts (with +-15V supply) Can someone tell me where my error might be?
Robert Brunnemer
2017-12-18 20:24:22 +0000 UTCSo the Lightbulb kinda acts like a thermistor close to or coupled to a heating element in series if i got this right. Could you emulate that lightbulb by wrapping a wire, for example one that is used in electric cigarettes around a thermistor? That way you could optimize, even tailormake the behavoir of your automatic gain control. You could even put down some celastic or heatglue to make it less sensitive to percussion. I would imagine that it would not be able to react as quickly to fluctuations at 1kHz as one downside and the resistance would be higher than the 36 Ohms you mentioned that bulb has.
Chris
2017-12-01 21:21:33 +0000 UTCI like how this oscillator works and is easy to make. A few months ago I did my own and work perfectly. For power supply I used a voltage doubler to get positive and negative voltage.
Elvis Baketa
2017-11-02 09:06:15 +0000 UTCIn an environment in which individual functionality was not deemed a generalized given; a Computer Operating System was observed to magically disappear or modify itself on its own very volition; a Hantek Digital Desktop Cro was shown to unexpectedly stop scanning; a Function Generator was better well bought. Psst! It seems that technology uneases an apparently bipolar Lord; within a realm where not even synthetic food was deemed truly worthy; or terribly good.
Frank
2017-10-29 14:59:56 +0000 UTCI don't have a dual power supply, so I used a spare TLE2426 rail splitter. Ran 30V into it, then used it's "out" pin as circuit ground. <a href="https://youtu.be/bQ6P943rAck" rel="nofollow noopener" target="_blank">https://youtu.be/bQ6P943rAck</a> Now I just need the correctly opamp and bulb, lol.
David McAnulty
2017-09-02 05:39:37 +0000 UTCHi Hunter. If you expand this post by clicking on the large title, then right below the number of likes, on the left side you will see "load more comments" click that a few times, then look for "Kai Bollue" You will see in red, "load 4 replies" click that and there is a really good explanation there with a "TI" data sheet as well, if you want more.
Mr Carlson's Lab
2017-07-19 07:51:46 +0000 UTCI was looking at Sams IC OP-AMP cookbook by walter g. jung and there's a good section on wien bridge oscillators pg. 367. There's a line that says "The attenuation of the Wien network at the frequency of oscillation is equal to 3." Can you expand on this. Thanks.
Hunter carmouche
2017-07-19 01:54:23 +0000 UTCHi Eddie, Yes, I bought a pair of 28V 40mA (cold resistance ~70R) in the UK from eBay (item # 390808042128). Please note that they have no base (just bare wires). I super-glued mine to a 3mm hollow nylon standoff to give it a good base :-)
Erik G
2017-07-15 13:51:48 +0000 UTCHey, Thats great Erik!
Mr Carlson's Lab
2017-06-26 10:36:47 +0000 UTCHi Paul, I'm pleased to say that the new bulbs (£1.90 a pair) arrived and the circuit produces a nice 1.050 kHz sine wave. This is despite a very dodgy breadboard and non-matching components. It does however need a 7.2V Pk-Pk Voltage (strange) to work. Thanks for all your help and a great little project. I will post something in the Community section. Edit: I've now added a trimmer to one of the resistors and am getting a very stable 1kHz sine wave :-)
Erik G
2017-06-21 10:20:11 +0000 UTCHi Eric, That was my previous schematic (oops) Rf is R1 on this schematic. I look forward to seeing your results when you get the bulb.
Mr Carlson's Lab
2017-06-19 14:44:29 +0000 UTCHi Paul, Many thanks for your reply. There is no "Rf" on the schematic that I can find. I'm assuming you may be referring to RT? In any event I have tried every possible adjustment of both trimmers. I suspect the bulb I'm using is the issue and have ordered a could of cheap 28V 40mA bulbs (can't afford shipping from Digikey or Mouser for the specified bulbs). It will be good experimentation . I seem to be so close, yet so far but at least I have a nice square wave :-)
Erik G
2017-06-19 08:03:05 +0000 UTCHi Eric. The adjustment of Rf on the schematic is crucial. If the filament cold resistance is too low, you may have issues obtaining a sine wave. Carefully adjust Rf while watching the scope.
Mr Carlson's Lab
2017-06-18 03:27:36 +0000 UTCI gave this a very quick try, using your value components (close but not precisely matched pairs as I don't have a sufficient quantity of resistors & capacitors to choose from) and 2 x 9V batteries (actually 8.4V & 8.3V) configured to give +/- voltage to the TL072. I used a fairy light bulb as that was all I had to hand. Result - a stable 450Hz SQUARE wave. Can't figure why I did not get a sine wave. Wonder if it something to do with the unequal +/- voltages or the light bulb I used?
Erik G
2017-06-17 11:33:59 +0000 UTCThe 9 Volt supply would mean different settings, and possibly different distortion readings as well. There is no reason it shouldn't work. If you build it, share it in the community section, I would like to see the results.
Mr Carlson's Lab
2017-06-17 00:31:48 +0000 UTCHi Paul, Just wondering how critical the 15V (+/-) supply is. Would it be possible, for example, to build this with a +/- 9V supply? Although obviously not ideal, it may then be possible to use 2 x 9V batteries.
Erik G
2017-06-14 11:44:13 +0000 UTCAh, now I get it: As you can never exactly trim the loop gain to 1, in linear theory the oscilation would either raise to infinite amplitude or die out. In practice we thus need something to limit the amplitude without causing (too much) distortion. The filament temperature implements a negative feedback on the loop gain, depending on the current amplitude. The important thing to understand is that the temperature change of the filament during one cycle is intended to be negligible, thus it does not induce significant distortion. You could thus also use a transistor instead of the light bulb whose base or gate is connected to the output through a sufficiently large low pass filter (and probably an inverter as we need negative feedback), right?
Kai
2017-06-13 21:10:05 +0000 UTCHi Paul, could you maybe explain a little more why the bulb is needed? You said (and wrote in here) that you use it because of the nonlinearity. Well, the theory says: If all is perfectly linear and a perfect sinus is put in, a perfect sinus will come out. Any nonlinearity leads to distortion. Now you specifically add a nonlinearity to _reduce_ distortion? The only explanation I can think of is that by this another nonlinearity is compensated? Obviously you do not want to make things too comlicated, but maybe you could in general go a little more into the nasty details? Or throw in a theory special for those not afraid of a some differential equations every now and then?
Kai
2017-06-13 20:36:05 +0000 UTCThats definitely in the plan .
Mr Carlson's Lab
2017-06-08 07:43:33 +0000 UTCCan you make a video on how to build a better curve tracer than what's available on the web? Also how to hook it up to an old oscilloscope? I have an old Paco oscilloscope (5Mhz, model S-50) and was thinking of turning it into a curve tracer
Rom Hunter
2017-06-08 00:28:20 +0000 UTCIf you go to the community section, there are lots of pix there from other builds.
Mr Carlson's Lab
2017-06-07 18:19:05 +0000 UTCYou're Welcome! Look up the schematic for the HP-200C resistance tuned oscillator. That would be a neat vacuum tube build.
Mr Carlson's Lab
2017-06-07 18:17:56 +0000 UTCBuilt the circuit, got it to work-ish. Only getting square waves. Not using bulb on video. Isnt there somewhere you can post your builds/results? Can't find it. Cheers.
Diabolical Artificer
2017-06-07 13:51:43 +0000 UTCJust about to build this but got to wondering about building it using valves as per Mr Hewlitt's patent. See - <a href="https://en.wikipedia.org/wiki/File:Wien_bridge_oscillator_schematic_from_Hewletts_US_patent.png" rel="nofollow noopener" target="_blank">https://en.wikipedia.org/wiki/File:Wien_bridge_oscillator_schematic_from_Hewletts_US_patent.png</a> Thanks for another grand video.
Diabolical Artificer
2017-06-07 11:42:22 +0000 UTCWhile calculating the cutoff frequency I like to use this: 159155/RC where R is in Ohms and C is in uF or R is in kOhms and C is in nF. I think the 159155 is easy to remember. I found this tip on Henrik Forsten blog: <a href="http://hforsten.com/" rel="nofollow noopener" target="_blank">http://hforsten.com/</a> I highly recommend his blog he makes amazing stuff (like DIY VNA!) and explains it very well.
Marek Tomczyszyn
2017-06-04 21:29:24 +0000 UTCMouser want £12 + vat for delivery unless order is for more than £33, Farnell (UK) want £15.95 +vat regardless of order value. Seems a bit pricey if you ask me unless you need other items and then buy from Mouser as I did.
Eddie Bray
2017-06-04 08:30:27 +0000 UTCAs current is applied to the filament in the bulb, the resistance goes up. When the filament cools, the resistance drops again. A resistor does not do this action.
Mr Carlson's Lab
2017-06-04 08:19:02 +0000 UTCThanks for this project, I will be building this. One thing I want to ask, maybe I missed it in the video somehow but, why the light bulb? What is the difference between using a light bulb and a compatible value resistor?
Bora Yurtoren
2017-06-04 07:57:36 +0000 UTCHi Michael, Thanks for your kind comment. The machine is an SR780. At the end of the video, there is a brief look at the distortion on the machine. (screen shot)
Mr Carlson's Lab
2017-06-04 03:05:47 +0000 UTCGreat project Paul. How were you measuring THD?
Michael Lloyd
2017-06-04 02:34:28 +0000 UTCThat Atwater sounds like a neat project!
Mr Carlson's Lab
2017-06-03 16:45:18 +0000 UTCThe PTC thermistor will be terribly temperature sensitive. Unless you want a temperature to amplitude controlled oscillator :^) I do strongly encourage you to experiment though.
Mr Carlson's Lab
2017-06-03 16:44:41 +0000 UTCGreat, looking forward to it!
Mr Carlson's Lab
2017-06-03 16:40:41 +0000 UTCAnd that's only the beginning!
Mr Carlson's Lab
2017-06-03 16:40:16 +0000 UTCMouser and Farnell both got those bulbs in stock, for the fellow Euro's playing along.. :)
Joachim Andersen
2017-06-03 15:50:59 +0000 UTCHi, I'm just wondering if it's possible to replace the light bulb with PTC ~80Ohm thermistor to get rid of vibrations' influence on our sinewave? It's hard to get these bulbs in UK anyway. Or maybe some sort of LED + LDR with a driving circuit?
Krzysztof Olszak
2017-06-03 13:39:59 +0000 UTCyou are correct punch the numbers into a calculator and see what answer you get. Paul converted the 1 over 2 x Pi into a decimal ie 0.159 this is a constant meaning the value will never change. You are then left with 1 over RC to sort out. You could multiply R and C divide it into 1 and get another decimal ie 4000. multiply the decimals 0.159 x 4000 = 636 (same ans). Paul did a bit of clever maths instead he knew that 0.159 multiplied by 1 over 0.00025 is the same as 0.159 divided by 0.00025. With maths the best way is the way that makes the most logical sense to you.
Smiggy
2017-06-03 12:23:16 +0000 UTCHi Eddie
john smith
2017-06-03 11:09:02 +0000 UTCLoved the video and the math behind it and even uncovered a 25 year long lost formula I forgot about. 1 over 2 pie RC. Just like riding a bike. The OP Amp is $1.43 for me and the bulbs $1.20. Ill order a few kits worth and get right onto a veroboard. Ill share the results when done.
Aaron Pell
2017-06-03 10:08:30 +0000 UTCI have just placed an order for some from the US, if anyone in the UK would like a CM7387 I can send them by 1st class post (once I've received them) for £2 a pop, let me know if you are interested at edbray@rocketmail.com. I will only have 6 available so first come first served.
Eddie Bray
2017-06-03 09:29:17 +0000 UTCNice job, Paul..! Btw... You really know how to build anticipation for future videos!
nj Phil
2017-06-03 07:13:02 +0000 UTCPaul, You lost me in the math. never my strong point. I thought every thing on the bottom line would be multiplied together, 628 * R*C then divided into 1 . Also the bulb through me a curve. I get the drift from you that it acts like a shock absorber to balance the harshness out of the waive form. can you go into that a little more. Thanks, Steve
Steve Crisp
2017-06-03 06:29:33 +0000 UTCHi Martin. Where did you get your CM7387? Still need to source one.
john smith
2017-06-03 06:26:57 +0000 UTCThere are ways to produce split rail virtual grounds, is it worth going into this topic for people that don't have dual power supplies available, so they can get the +15 GND -15 rails from a single supply? Another great project Paul parts on the way, the CM7387 lamp was not as available in the UK as I thought it would be ended up paying £2.29 ($2.95) how does that compare in the US?
Smiggy
2017-06-03 06:06:55 +0000 UTCI checked my op amps and they were tl082 so I ordered some 72's
Hunter carmouche
2017-06-03 03:57:19 +0000 UTCOh man, that was a close one. All my stuff is 12 volts. So I was online looking at circuits and breadboards when I stumbled upon a breadboard that looked like one I got off eBay years ago, A/D trainer PAD-234A. Looked at the specs and lo and behold variable 15 volts. Have to be careful because it will go higher. Just checked it on the volt meter. Went to an estate sale a week ago and picked up an 1935 Atwater Kent 286 totally roached, so far all coils check. Now to find out what is what. Bring it on....hehehe.
Hunter carmouche
2017-06-03 03:54:27 +0000 UTCIf you need a differential power supply suitable for this and many other op amp experiments there is a simple power supply kit available from Jameco: JE215 Dual-Output Adjustable Linear Regulated Power Supply, ~$30. It provides +/- 15 volts. I added a switch and a fuse on the line side of the power transformer. Yes, the kit has an unfused input... otherwise it's a straightforward device.
allenc
2017-06-03 03:51:20 +0000 UTCNo problems Troy, I will cover your question and much more about this topic, were really just getting started. To give you the quick answer, the output impedance of an op amp in most configurations is quite low. The output of the TL072 will drive a 2K Ohm load with no noticeable clipping at full output. If you drop the output down to 15Vp-p, you can drive 400 Ohms with no noticeable clipping on an oscilloscope. To couple this into a tube circuit, a simple termination and suitable DC blocking capacitor can be used. Hope this helps :^)
Mr Carlson's Lab
2017-06-03 01:44:40 +0000 UTCWhat is the output impedance of this circuit, wouldn't it have to be low in order to drive a variety of loads or am I way off on my thinking and will it cause the open circuit voltage to decrease when loaded. I have been with a bit of struggle figuring out load matching, attenuation and such. If I am jumping ahead too far, please say that we will cover that in the future and I will wait patiently. Thanx Mr. C
Troy Pelton
2017-06-03 01:18:55 +0000 UTCLOL, I don't mean too :^)
Mr Carlson's Lab
2017-06-02 22:38:55 +0000 UTCCrazy butterfly effect. Be sure to put your part orders in before the videos come out. Paul is driving prices up!
Mark Bosse
2017-06-02 20:56:22 +0000 UTCHey Andre, this area is the Posts section, which will be highlighted in Orange on your screen. On the left of it would be the Overview section, to the right of it, the Community section, both of which would be Gray at the moment. Once you click the Community link it will turn Orange. If you don't see them right away, scroll to the top of the page and you'll find them just underneath the main Mr Carlson's Lab banner image and to the right of the inset picture of Mr Carlson's profile picture. Hope that helps!
Paul F. De La Cruz
2017-06-02 17:15:23 +0000 UTCif the order is more than £33 they (usually) send with free shipping . I placed an order on Tuesday evening (UK time) this week, it was delivered on Thursday at 12:20pm. Better service than from some of the UK component suppliers.
Eddie Bray
2017-06-02 16:47:21 +0000 UTCYep, I've just spent ages trying to find a UK supplier, might have to wait until my next Mouser order, they have them for 96p each (+vat) with no minimum order. If anyone is unaware, Mouser send stuff from Texas with Fedex
Eddie Bray
2017-06-02 16:43:39 +0000 UTCOne more thing... Where can I find the community section?
Andre Gopee
2017-06-02 16:30:07 +0000 UTCThank You Paul for this video, I have look on many site to find out about this equations and you explained it so very well. I have also learned some more about gain control and how to measure it. I will order these parts and build it on a circuit once I complete it on the Bread board. Thanks you for sharing your knowledge with us. Can wait for more.
Andre Gopee
2017-06-02 16:28:38 +0000 UTCChristmas lights it is!
Mr Carlson's Lab
2017-06-02 15:13:11 +0000 UTCOk I have just received a reply from ebay supplier (Jam-sales) He wants $48 postage to send two bulbs. Farnell wants $19.83 postage. there is no uk supplier.
john smith
2017-06-02 14:44:17 +0000 UTCTime to do some experimentation, break out the old incandescent Christmas lamps :^) I find it hard to believe that a CM7387 or the 7380 bulb can't be ordered in the UK.
Mr Carlson's Lab
2017-06-02 14:31:56 +0000 UTCThanks for your kind words Reb! I'm looking forward to seeing your build.
Mr Carlson's Lab
2017-06-02 14:20:24 +0000 UTCThe bulb is not available in the UK. and I am unable to find an equivalent.
john smith
2017-06-02 14:16:45 +0000 UTCHi Steve, I'm glad to see that I have introduced you to something different and new. There will be a lot of that here. The bulb in the circuit acts as an AGC or automatic gain control. You will see a variable resistor from pin 1 to pin 2, and from pin two to ground is the bulb. This arrangement forms a Voltage divider to pin 2. A light bulb acts as a non linear resistance. As it heats, the resistance goes up, therefore changing the ratio of the Voltage divider "Automatically." If the resistance of the bulb is low to begin with (cold) more current will be required to cause the AGC action. A higher cold resistance bulb will act in a more sensitive manor, as not so much current is required for that AGC action. So in short: Higher resistance bulb requires less drive to make the AGC action work, less drive means the op-amp has an easier job supplying the current to make this action happen, this equals less distortion.
Mr Carlson's Lab
2017-06-02 14:15:02 +0000 UTCCan you explain why you use a light bulb and not a simple resistor? Is it because the circuit needs the inductance of the filament? Is it possible to explain how the circuit work? It is strange to me to use a light bulb for a purpose other than producing light.
Steve Beaudoin
2017-06-02 11:10:52 +0000 UTCPerfect Video, wow! Not only that you're providing useful circuits, there are so many useful informations besides the way, to learn how this example works. I have ordered the tl072cp, the bulbs and hope they will arrive soon. This is a great way you provide. Many thanks Paul!
Reb Elba
2017-06-02 10:23:02 +0000 UTCHi Zen. You sure can.
Mr Carlson's Lab
2017-06-02 04:48:18 +0000 UTCThis is awesome this solves my short term signal generator issue. I can use this to feed the transistor bias circuit.
Zenwizard
2017-06-02 04:09:31 +0000 UTCThanks Larry! I'm looking forward to reading about your project.
Mr Carlson's Lab
2017-06-01 22:46:04 +0000 UTCexcellent job Paul. can't wait to build this weekend..
Larry H
2017-06-01 21:13:57 +0000 UTCDon't forget to share your results in the community section, I would love to see your versions! A post will be coming soon with PCB layouts for this as well. See you soon!
Mr Carlson's Lab
2017-06-01 20:32:55 +0000 UTC
