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Generating square waves of 0-5V voltage levels

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Hi there, I have a problem with my circuit. I suppose to get a square wave output with voltage levels 0-5V at point A, but when I test my circuit with the circuit maker simulation, it gives me a different answer. What should I need to do in order to get the desire output?
 

The way that that circuit is. Point A is going to be offset above ~ 2.5(800k/1000k) V .There are all kinds of problems with that circuit . Transistor Q2 is driving a lot of current that is not even needed !!!!!!! I still don't get what is the point of that output cap the OUTPUT WILL BE OFFSETTED OF 2.5 V so whatever you will get in the output it never will 0 to 5 V ..


Ps : all that you need is a signal clipper to trim the input sine sine signal and a schmidt trigger to square up the signal .!

I just found another BIG !!!!!!1Problem . The polarization resistor R1 at the gate of the FET will never provide enough current to turn ON the DIODES .The FET gate has a SEVERAL HUNDRED megs resistance )
SO BASICALY THIS THING IS NOT WORKING!
 

because Q2 B-E only 0.65V ,so R3 only have same 0.65V voltage,But Q1 want to saturate turn on,But 5V=V_R3+VDS_Q1+V_R5,and R5 have smaller voltage than R3,so the equation is not realize.and so you design idea of 0-5V is not realize.
 

eltonjohn said:
I just found another BIG !!!!!!1Problem . The polarization resistor R1 at the gate of the FET will never provide enough current to turn ON the DIODES .The FET gate has a SEVERAL HUNDRED megs resistance )
SO BASICALY THIS THING IS NOT WORKING!
Click to expand...

How should I modify it to turn on the diodes?

eltonjohn said:
Ps : all that you need is a signal clipper to trim the input sine sine signal and a schmidt trigger to square up the signal .!
Click to expand...

Can you help me on that? You have any relevant circuit? Thank You :)
 

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