Hello everyone, im going to use this circuit in my laboratory design project and represent the duty cycle as an output. My problem is that as a final report they want the analysis of the circuit we used. Thus I need an analysis of the Op-amp square wave generator part. I will be happy if anyone could analyse the circuit and write the frequency and duty cycle dependence on circuit component as mathematical expressions. Thank you very much..

 

Keyword : Hysteretic Oscillator

Look it up on Wikipedia. I have an article about a similar approach here.

The AAC book also has a chapter on it here.

 

If you study comparator circuits with hysteresis using positive feedback, you will easily be able to develop the analysis of this circuit.

 

The lousy old 741 opamp is 40 years old this year. It is too slow for a square-wave generator. Frequencies above only 9kHz will be a low level triangle-wave.

 

hi there
i tried ur circuit and it didn't oscillate,, r u sure its the correct one

 

Many old 741 opamps do not work when the supply is only 5V. Try 12V or 15V.
Turn the positive feedback pot for a high amount of positive feedback and turn the negative feedback pot for a low amount of negative feedback.
Adjust the reference voltage pot to half-way.
Then it will oscillate.