Really great explanation of the astable multivibrator (at least that's the name I learned for this circuit). I appreciate the storytelling involved in the video explaining why the old configuration wouldn't work. When I first took Electronics I this circuit gave me so much trouble, and your explanation would've helped out tremendously.

Another awesome video. I use this circuit when I want a cheap and dirty (variable frequency) PWM. Since the PID function can be solved in a single op amp, an LM358 can be used as a complete PID/PWM system and tuned with the Ziegler-Nichols method. edit- I should add, to hack this circuit for PWM start by changing the value of the resistor of the 9 volt to positive node from 100K to a lower value. Try using 10k as a starting point with a 10K pot.

I like this kinds of things, like you do not want to add an additional chip to your circuit just for an oscillator in all cases

this is the greatest video ever

I have been fighting with op amps all week trying to get them to oscillate with no success and i just stumbled upon this lesson and hey presto.....i am getting a waveform, not a very clean one and it doesn't go rail to rail but at least i have some activity....thankyou for this, i am ecouraged

triangle wave relaxation oscillator on the cheap. kewl. nice workaround for single ended.

Thank you for your patience.

thank you

Thanks for the very intuitive introduction and I wish I had seen your video earlier when I first started designing my own circuit as a hobbyist. I always love this type of astable multivibrator over 555 ones since most 555 timer ICs require 5V and a few mA current, but this one, as there are a wide selection of opamps, one can build oscillators with extreme features, such as - very low supply voltage (as low as 1.5v) very low power (I even tried 800nA range using nanoAmp opamps, very tiny capacitor and very large (a few Mohm) charging resistor) high frequency (1MHz using high GBWP opamps, or very fast comparators).

@copernicofelinis

2 жыл бұрын

A bjt astable multivibrator can go down to little over 0.7 volts (it still oscillates even under threshold, but to a different frequency).

@sullivanzheng9586

2 жыл бұрын

@@copernicofelinis Sure, that totally make sense. And I wondered what oscillator would operate with even lower voltage, like 200mV or something? Since I saw quite a few energy harvesting ICs which are basically very very low voltage DC-DC boost converter. To start with such IC needs to have oscillator working with very low voltage. Don't know how that was achieved.

@sullivanzheng9586

2 жыл бұрын

@@copernicofelinis My guess could be a JFET oscillator since for JFET it can be biased to amplification region even when Vgs = 0. While BJT and MOSFET requires significant higher bias Vgs/Vbe

@absurdengineering

2 жыл бұрын

@@sullivanzheng9586 Mosfets configured to have zero or close to zero threshold voltage will do it. Or any mosfet in subthreshold operation.

@sullivanzheng9586

2 жыл бұрын

@@absurdengineering You mean the classic 2 mosfet multivibrator with their drain coupled to each other's gate via capacitors?

Great Tutorial, I would like to experiment with opamps and was wondering if you have a schematic of Diy dual rail power supply. adjusting both outputs with the same control ?

@IMSAIGuy

2 жыл бұрын

That is called a dual output tracking supply. I would do something like the first schematic here: www.eevblog.com/forum/projects/linear-power-supply-with-multiple-outputs/ use a potentiometer with dual wipers.

You probably should put those "V" in quotation marks. Only for rail-to-rail opamps is this very close to V. Most are about 2 V away and many are not even symmetric. You can improve the symmetry and accuracy of your waveform greatly in most cases using an output resistor and two matched Zener diodes inverse series to ground.

nice. 👍

You said single supply but shown two polarity supply with separate ground.Why?

@IMSAIGuy

2 жыл бұрын

did you watch the entire video? I show both types

@tnamen1307

2 жыл бұрын

@@IMSAIGuy please help. Its urgent. I used lm358 as oscillator pulse wave generator by providing 12V DC. I provide extra resistor R to the positive pin of the op amp as described in your video. All resistors used are of value 1 KOhm, total 4 resistors. However, surprisingly, the op amp does not work. It does not give out even a mere 12 V. Rechecked the circuit, but still no results. Now, very contrastingly, with still maintaining the same circuit, I changed all the values of R to 10 KOhm, total 4 resistors. At this point, the op amp generates PULSE SQUARE WAVE. So, my request is to make new videos why OP AMP does not work on resistors of 1 KOhm. But work on 10 KOhm. Thanks.

thanks for your interesting video. would you please tell me : 1.which opa you use? 2.the value of the capacitance? I want to implement it. thank you!

@IMSAIGuy

Жыл бұрын

LM324 100K 3.9nf here it is: kzread.info/dash/bejne/oKaXyrp_Z5rTlJM.html

How do you calculate the frequency for this one? I tried the usual 1/2piR_cC as well as using the formula for the dual supply, the one with the 2RCln(2R_2/R_1), they are giving me values that don't agree with my simulation.

@IMSAIGuy

2 жыл бұрын

Yes. Those won't work. You need to solve for the upper trip voltage and lower trip voltage. I don't feel like doing the math.

@tnamen1307

2 жыл бұрын

​@@IMSAIGuy hello, I used lm358 as oscillator pulse wave generator by providing 12V DC. I provide extra resistor R to the positive pin of the op amp as described in your video. All resistors used are of value 1 KOhm, total 4 resistors. However, surprisingly, the op amp does not work. It does not give out even a mere 12 V. Rechecked the circuit, but still no results. Now, very contrastingly, with still maintaining the same circuit, I changed all the values of R to 10 KOhm, total 4 resistors. At this point, the op amp generates PULSE SQUARE WAVE. So, my request is to make new videos why OP AMP does not work on resistors of 1 KOhm. But work on 10 KOhm. Thanks.

@tnamen1307

2 жыл бұрын

hi, please check your project by replacing all resistors with value 1 KOhm. Your op amp will not work.

Thank you so much, I can finally build a circuit out of shit, so other hobo's can't steal the shit behind my back.

Do you know any simple oscillator circuit that transfers the charge back and forth instead of dissipating it for every cycle? Thank you very much.

@RexxSchneider

2 жыл бұрын

If you use a resistor as a timing element, you will dissipate the charge. That implies that you need to use a tuned LC circuit to create your oscillator. You can Google for "op amp LC oscillator" or for the terms "Colpitts" or "Hartley" and turn up many examples.

@IMSAIGuy

2 жыл бұрын

Rex is correct. there are relaxation oscillators or resonate oscillators. search for resonate LC or also crystal oscillators.

@absurdengineering

2 жыл бұрын

Try playing with this and get an inductor and see where you can put it to get it to oscillate :) Rediscovery can be quite thrilling because it’s all new for you!

Do you have a tutorial for a function generator by chance?

@IMSAIGuy

10 ай бұрын

this might be what you are looking for: kzread.info/dash/bejne/rJZ-o8Rwmrm4ftI.htmlsi=TZ9mHi5zt49bLLOv

@johnsmith-lb4mo

10 ай бұрын

@@IMSAIGuy Thankyou so much, i will play when i get a chance.

LM358 does not work on 1 KOhm for square pulse generator. I used lm358 as oscillator pulse wave generator by providing 12V DC. I provide extra resistor R to the positive pin of the op amp as described in your video. All resistors used are of value 1 KOhm, total 4 resistors. However, surprisingly, the op amp does not work. It does not give out even a mere 12 V. Rechecked the circuit, but still no results. Now, very contrastingly, with still maintaining the same circuit, I changed all the values of R to 10 KOhm, total 4 resistors. At this point, the op amp generates PULSE SQUARE WAVE. So, my request is to make new videos why OP AMP does not work on resistors of 1 KOhm. But work on 10 KOhm. Thanks.

@IMSAIGuy

2 жыл бұрын

the LM358 is a slow opamp. changing from 1k to 10k slowed the oscillation down by a factor of 10