Opamp filter - oscillator

Thread Starter

xxxyyyba

Joined Aug 7, 2012
289
We are studying opamps right now so it's probably opamp :)
I started thread by mistake here, it should be in homework category...
 

MrAl

Joined Jun 17, 2014
7,757
Hello. Here is my task:

View attachment 94943

How to solve this? I'm confused because of only one input in opamp.
Hi,

What you would do is first write out the transfer equation which of course includes the gain A, then solve for the A that makes one or more of the poles cross the jw axis into the right hand plane of the complex frequency plane. The input doesnt even matter that much but you probably assume that is a stable input, like a unit step.

I have to assume that you know how to write the transfer equation or i could not see how this question could have been asked of you, unless you missed a lecture or something :)
 

Thread Starter

xxxyyyba

Joined Aug 7, 2012
289
To find loop gain, we cut feedback and apply test generator like this:

dzeks1.png


dzeks1.png

Then we use conditions Re{Abeta} >=1, Im{Abeta}=0, to find A, right?
 
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