I am no expert on the fine points of Wien bridge oscillators, but have built many that use just the basic configuration, with the addition of any of the simple amplitude control features, such as incandescent light bulbs (not just ANY light bulb), or reverse-parallel LEDs, etc. I don't like the incandescent bulb approach because of its microphonic effects. I am not thrilled with the LED method either, as the circuits I have made using those seem to have less sine wave symmetry. As I recall from my electronic circuit theory courses many decades ago, the primary key to low sine wave distortion in these circuits is the quality of the amplitude stabilization part. That, and how closely the two RC portions match, as they form a pair of low-pass and high-pass filters, and between them in the bridge circuit they form a band pass filter, with the center of the filter frequency being the best oscillation frequency, and best stability. I mostly used these to be "precision" sine wave signal sources for calibrating older analog recording equipment and testing recording studio equipment and signal paths. I never had access to a good distortion analyzer, and had to just use my eyes on an oscilloscope display of the waveform. I got pretty good at being able to spot asymmetry (at least I THINK I was good at it). But I was always amazed at how many people would look at obviously asymmetric "sine waves", or even triangle waves with some filtering to make their points a bit rounded, and they would pronounce those to be "clean sine waves". When I used to build these, I always tried to use high quality capacitors, and bought ones with good stability characteristics, and good accuracy specifications, then used a capacitance meter to match them in pairs. I did the same with the two resistors used in conjunction with the capacitors. Doing that gave me my best results, at least using the old eyeball THD test.
When you were doing the Tek plugins, I was wondering if you'd do the SG505. So I looked up the price of them - way too high unless one somehow fell into your lap. The SG505 is actually a State Variable Oscillator and is an interesting study case on how to optimise a circuit and does interesting things with the venerable NE5534A opamp. Maybe wrong but ISTR that Jim Williams might have had something to do with it? Edit: I was wrong, Jim Williams was not involved in the design of the SG505, at least not according to Bruce Hofer who led the team that did.
Actually you CAN change just one side and change the frequency fairly easily. It takes a little experimentation, but it's not difficult. I can't remember, but I think it was on the non inverting input, but don't hold me to it. I have no way to check distortion, but it looks clean on the scope. SO many pieces of test equipment can be made with this! Thank you for sharing.
Very nice simple circuit, a long time ago there was a custom made part for that light bulb element, it was the R53 ntc thermistor, they're long obsolete but still remain the simplest cheapest was of stabilising this type of oscillator.
Yay! That's a happy coincidence. Note that re my previous question about the TI TL07x/8x JFET input opamps: I figured out my confusion. As of 2020 or thereabouts, TI's making the 7's and 8's almost indistinguishable, and getting rid of the 1977 "BiFET II(tm)" inputs which were neat; for their tolerance for ESD, and the THD. This is to "get their customers to move to new technology", which is unfortunate because they don't have this application in mind, and the price was right. I have a pet project with these oscillators, if not obvious. I've wanted to make the cheapest, cleanest signal injector for audio work possible, with a monitor out for scopes and a probe to inject the same signal. Ultimately, if you hook up everything, you'd have 2 channels of 0.03% THD sine wave, and 2 channels of whatever part of the circuit you're fuzzing. Much better than the buzzer noise types and almost as cheap. I'd love for the world to have a cheap, floating, and safe tool for that sort of work. The "floating" bit being key, with live DUTs and instruments being a dangerous combination, obviously. One more note about HP history: the HP200A used variable capacitors (and discrete valves, of course), but the economics reversed since then, so it's pretty much impossible to design it that way now. And it's nicer, to boot, to use a ganged resistor or stepped attenuator; my prototype has both (or three), as you need lots of turns in its lifetime, and you need _lot_ of range as far as resistance to do 20 to 20k (or nicer); so it's the old "range selector plus coarse and fine" design. Very happy you covered one of my favorite cheap circuits, _and_ used the "bridge notation"! And not to appear like I have any advanced knowledge compared to your vast experience, I'd love to hear any history or notes you have, if you find the time. Thanks again for covering this one.
You can adjust the frequency by adjusting any of the individual components, but the analysis is much easier of the resistors and capacitors are the same. You also probably aren't going to get much range in frequency adjustment by just changing the resistance, and the gain will need to be compensated as well (which makes it easier to adjust the frequency if you already have an amplitude servo loop.
So glad you stated on your last video about the math,cause I got married off n was just starting fractions and my next to oldest brother had same teacher year before n i can't tell you how many times i was told to leave the room for raising my hand to asked a question lol. But my dad taught me how to use oscilloscope and signal generator. But seriously what types of math do you really need?
Have you tried several different 5.1k to 10k combinations? Was it always stable oscillating? How large was the output signal and the output signal differences for several combintions? I am a little bit surprized because the voltage amplification is a little bit lower than 3. I would have be expected that it needs to be a little bit more than 3 to start continuously oscillating. The maximum output voltage will limit the voltage amplification to 3. The more amplifiction you set with the voltage divider, the more the signal will turn into an rightangular shape.
You have been doing some circuit investigations, lately. I am enjoying this content. Thank you for sharing. I have ordered the 10MHz OXCO modules that you featured recently. I plan to tie it to my DIY GPS clock to make a GPSDO. noobEE Question = Would placing a Wien Bridge Oscillator somewhere in the circuit be of benefit? If so, how would it be employed? Please and thank you.
Great oscillator for low frequency, but since it has two Cs it is hard to do VCO with it. I guess, we could change Rs with a transformer and have one C (vractor) from positive input to ground. Then we can have VCO. As you know then the Frequency will be 1/(2PI(SQRT(LC))
Does anyone know how to make a VCO out of this circuit? I experimened and learned a lot from this simple circuit. In 80s I wanted to make a PLL signal generator. But I ended up using a SRAM (EPROM later on) which then I could easily change the frequency and amplitude.
Can someone explain why the frequency changes based on the voltage fed into the Op Amp? At +/- 9v I get 1.666kHz. At +/- 3.3v I get 1.718kHz and there is a steady progression of increase in frequency with reduction in supply voltage.
@@IMSAIGuy Ah of course. I saw this impact when converting the Sinewave to a Square wave via a 74HC14 but failed to take into account the circuit inside the Op Amp. It does, however throw a little spanner in the works for trying to calculate the expected f based on R and C. I guess its near enough as a start point then test and adjust.
No, but it does change the amount of gain you need to get oscillation. And controlling the gain is a big issue in how much distortion you get, hence the reason for controlling the gain using either a lightbulb or more complex feedback loop.
@@jms019 I specifically mentioned "high quality"; C0G/NP0 dielectric can measure up to even the best film dielectrics in terms of voltage coëfficiënt, temperature stability, aging, etc. The downside is that they are only available in relatively small values.
A pair of 1N4148 diodes also work well instead of a FET or a light bulb.
Hello, there is beauty in simplicity 👍 thanks
Nice day 🙂 Tom
Thanks. Love these experimental posts. Please think up more if you can.
I am no expert on the fine points of Wien bridge oscillators, but have built many that use just the basic configuration, with the addition of any of the simple amplitude control features, such as incandescent light bulbs (not just ANY light bulb), or reverse-parallel LEDs, etc. I don't like the incandescent bulb approach because of its microphonic effects. I am not thrilled with the LED method either, as the circuits I have made using those seem to have less sine wave symmetry.
As I recall from my electronic circuit theory courses many decades ago, the primary key to low sine wave distortion in these circuits is the quality of the amplitude stabilization part. That, and how closely the two RC portions match, as they form a pair of low-pass and high-pass filters, and between them in the bridge circuit they form a band pass filter, with the center of the filter frequency being the best oscillation frequency, and best stability.
I mostly used these to be "precision" sine wave signal sources for calibrating older analog recording equipment and testing recording studio equipment and signal paths. I never had access to a good distortion analyzer, and had to just use my eyes on an oscilloscope display of the waveform. I got pretty good at being able to spot asymmetry (at least I THINK I was good at it). But I was always amazed at how many people would look at obviously asymmetric "sine waves", or even triangle waves with some filtering to make their points a bit rounded, and they would pronounce those to be "clean sine waves".
When I used to build these, I always tried to use high quality capacitors, and bought ones with good stability characteristics, and good accuracy specifications, then used a capacitance meter to match them in pairs. I did the same with the two resistors used in conjunction with the capacitors. Doing that gave me my best results, at least using the old eyeball THD test.
When you were doing the Tek plugins, I was wondering if you'd do the SG505. So I looked up the price of them - way too high unless one somehow fell into your lap. The SG505 is actually a State Variable Oscillator and is an interesting study case on how to optimise a circuit and does interesting things with the venerable NE5534A opamp. Maybe wrong but ISTR that Jim Williams might have had something to do with it?
Edit: I was wrong, Jim Williams was not involved in the design of the SG505, at least not according to Bruce Hofer who led the team that did.
Nice video. Thank you !
Actually you CAN change just one side and change the frequency fairly easily. It takes a little experimentation, but it's not difficult. I can't remember, but I think it was on the non inverting input, but don't hold me to it. I have no way to check distortion, but it looks clean on the scope. SO many pieces of test equipment can be made with this! Thank you for sharing.
Hi, there is beauty in simplicity 👍 Thank you Best Regards...!!
Very nice simple circuit, a long time ago there was a custom made part for that light bulb element, it was the R53 ntc thermistor, they're long obsolete but still remain the simplest cheapest was of stabilising this type of oscillator.
Ah, yes, the RA53! Managed to buy a couple of them about 25 years ago. They work amazingly well.
Yay! That's a happy coincidence. Note that re my previous question about the TI TL07x/8x JFET input opamps: I figured out my confusion. As of 2020 or thereabouts, TI's making the 7's and 8's almost indistinguishable, and getting rid of the 1977 "BiFET II(tm)" inputs which were neat; for their tolerance for ESD, and the THD. This is to "get their customers to move to new technology", which is unfortunate because they don't have this application in mind, and the price was right.
I have a pet project with these oscillators, if not obvious. I've wanted to make the cheapest, cleanest signal injector for audio work possible, with a monitor out for scopes and a probe to inject the same signal. Ultimately, if you hook up everything, you'd have 2 channels of 0.03% THD sine wave, and 2 channels of whatever part of the circuit you're fuzzing. Much better than the buzzer noise types and almost as cheap. I'd love for the world to have a cheap, floating, and safe tool for that sort of work. The "floating" bit being key, with live DUTs and instruments being a dangerous combination, obviously.
One more note about HP history: the HP200A used variable capacitors (and discrete valves, of course), but the economics reversed since then, so it's pretty much impossible to design it that way now. And it's nicer, to boot, to use a ganged resistor or stepped attenuator; my prototype has both (or three), as you need lots of turns in its lifetime, and you need _lot_ of range as far as resistance to do 20 to 20k (or nicer); so it's the old "range selector plus coarse and fine" design.
Very happy you covered one of my favorite cheap circuits, _and_ used the "bridge notation"! And not to appear like I have any advanced knowledge compared to your vast experience, I'd love to hear any history or notes you have, if you find the time. Thanks again for covering this one.
You can adjust the frequency by adjusting any of the individual components, but the analysis is much easier of the resistors and capacitors are the same. You also probably aren't going to get much range in frequency adjustment by just changing the resistance, and the gain will need to be compensated as well (which makes it easier to adjust the frequency if you already have an amplitude servo loop.
Neat low distortion sine for an amplifier test...cheers.
Thanks for this Nice video, can you please do a video about temperature sensor adaptive circuit?
So glad you stated on your last video about the math,cause I got married off n was just starting fractions and my next to oldest brother had same teacher year before n i can't tell you how many times i was told to leave the room for raising my hand to asked a question lol. But my dad taught me how to use oscilloscope and signal generator. But seriously what types of math do you really need?
Have you tried several different 5.1k to 10k combinations? Was it always stable oscillating? How large was the output signal and the output signal differences for several combintions?
I am a little bit surprized because the voltage amplification is a little bit lower than 3. I would have be expected that it needs to be a little bit more than 3 to start continuously oscillating. The maximum output voltage will limit the voltage amplification to 3. The more amplifiction you set with the voltage divider, the more the signal will turn into an rightangular shape.
Nice 👍
You have been doing some circuit investigations, lately. I am enjoying this content. Thank you for sharing. I have ordered the 10MHz OXCO modules that you featured recently. I plan to tie it to my DIY GPS clock to make a GPSDO. noobEE Question = Would placing a Wien Bridge Oscillator somewhere in the circuit be of benefit? If so, how would it be employed? Please and thank you.
no
Great oscillator for low frequency, but since it has two Cs it is hard to do VCO with it.
I guess, we could change Rs with a transformer and have one C (vractor) from positive input to ground. Then we can have VCO. As you know then the Frequency will be 1/(2PI(SQRT(LC))
Does anyone know how to make a VCO out of this circuit? I experimened and learned a lot from this simple circuit. In 80s I wanted to make a PLL signal generator. But I ended up using a SRAM (EPROM later on) which then I could easily change the frequency and amplitude.
www.edn.com/building-a-jfet-voltage-tuned-wien-bridge-oscillator/
Cool. Experiment time!
hey buddy! U know U could make this better, by assuring Quality part usage!! good luck !
Can someone explain why the frequency changes based on the voltage fed into the Op Amp? At +/- 9v I get 1.666kHz. At +/- 3.3v I get 1.718kHz and there is a steady progression of increase in frequency with reduction in supply voltage.
it varies the hysteresis trip point
@@IMSAIGuy Ah of course. I saw this impact when converting the Sinewave to a Square wave via a 74HC14 but failed to take into account the circuit inside the Op Amp. It does, however throw a little spanner in the works for trying to calculate the expected f based on R and C. I guess its near enough as a start point then test and adjust.
So if you don’t have the R and C the same, you get an asymmetric sine wave (more distortion)?
No, but it does change the amount of gain you need to get oscillation. And controlling the gain is a big issue in how much distortion you get, hence the reason for controlling the gain using either a lightbulb or more complex feedback loop.
How did you measure THD?
The Keithley 2015 multimeter has a THD measurement
@@IMSAIGuy do you know how THD is measured without using digital FFT and microprocessors?
@@bayareapianist yes, the older instruments (HP 334A) use a notch filter to remove the carrier, then sum up what is left.
@@IMSAIGuy I saw one on eBay for sale now. I think it's a good material for your channel if you don't have one.
great, you can have it shipped to me
now demo with SA! ;-}
Don’t use ceramic capacitors for anything like this.
High quality ceramics like C0G/NP0 are perfectly usable in an oscillator like this.
I was more concerned with the non-linearity. Actually testing this would make a good experiment for our host.
@@jms019 I specifically mentioned "high quality"; C0G/NP0 dielectric can measure up to even the best film dielectrics in terms of voltage coëfficiënt, temperature stability, aging, etc.
The downside is that they are only available in relatively small values.
I recommend Application Note 43 of Linear Technology (PDF for download). Complex Gain regulations for ultra low distortion !