PSpice Simulation Problem (not the desired ouput)

Jun 10, 2010 2 Replies

Hello all!



I am trying to simulate a circuit from a book called "DESIGN AND DEVELOPMENT OF MEDICAL ELECTRONIC INSTRUMENTATION : A Practical Perspective of the Design, Construction, and Test of Medical Devices " by DAVID PRUTCHI and MICHAEL NORRIS.



This is the circuit:



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In the book they say that the output at the heart (see the picture) should be:



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But I don't get any output in that point, the voltage is 0 continuosly:



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I tried to check the voltage in a point after the oscillator part, and the output is a constant aprox 2.2 V, so I guess the oscillator part is not working properly, and I don't know what the problem is. Maybe something should be changed, added.



Can somebody tell me, by looking at the circuit, if the oscillator part looks OK or not?



If anybody uses OrCad and wants to try a simulation of the circuit, I uploaded the OrCad project for you:



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Please anybody help me. Would be so appreciated.



Thank you



PS: the book doesn't provide much more information about the circuit than what I told you, but if anybody wants to take a look at the book just tell me and I will upload it for you.



Cheers


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Looks like Q2 base and collector are shorted.

I simulated it in ltspice with Q1's collector and Q2's base connected to each other and connect to nothing else and it then oscillates (pulses).

So C1 does not connect to Q2's base and Q1's collector doesn't connect to Q2's collector.

Likely a typo where the wires crossed...

Thank you so much mike!

Cheers

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