# OPAMP multivibrator help

Could someone tell me how can I calculate resistors and capacitors?

I dunno… My calculus is very rusty. Maybe try [u]this circuit[/u]. Or, do the usual thing and use an [u]LM555[/u].

That is the astable opamp multivibrator, I know how to calcule that, I think it´s not the same thing! This circuit it´s for a school work and I can´t find any formula for this.

This should help:

http://www.electronics-tutorials.ws/oscillator/rc_oscillator.html See the section labled Op-amp RC Oscillator Circuit

By the way that was the second link offered by googling RC oscillator

Lefty

My circuit has resistores on top, is it the same thing?

If you had done the OBVIOUS and Googled a "Phase Shift Oscillator" and it is a classic circuit used to teach many things... Electronic but not generally ever digital You would have found the WIKI reference to it... I'm reasonably certain that this circuit isn't intended to teach phase-shift, transistor biasing (It is a class A amplifier too) or oscillator theory in general. So I am somewhat taken aback that either your instructor didn't even name the circuit... Or you didn't take the time to write it down.. It was the first transistor oscillator I ever built and the first transistorized device I made... BTW the Wiki article is a good one with the necessary math...

the resonant frequency formula is different

Bob

My instructor gave the name but I don´t know how to translate all the name.

Well, young person... it was obvious to my tired old eyes that it was a homework assignment that you were late for and had you been a "little more careful... you would have the assignment done already. As a general rule I don't offer to help with work of that nature. There are several good lessons in that circuit involving various aspects of electronics from calculating feedback networks to transistor biasing... But IF you get stuck you can leave the message here and PM me that it's here or just PM.. But I prefer to, if possible answer here as everyone can benefit? from my answer. I now more fully appreciate the language differences and I will be most careful to be clear and precise.

Bob

ok, if I have questions I ask here!

faurek: ok, if I have questions I ask here!

You can certainly ask questions here, and usually get good help, however, too many people come here "first" when they could do a 30-sec google search, and find the answers immediately.

The most common sin is, many people are too darn lazy to simply find the datasheet for some part, and look inside.

Then, after doing a search, if you don't understand something you can ask about the specifics of that, once it's clear you've actually tried to find the answer yourself. Better to learn how to fish than simply ask for a free fish. Then, oldtimers will see you in a smarter perspective too. Yes?