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From: electro_1 on 10 Jun 2010 11:00
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:

http://img571.imageshack.us/img571/6449/fig4.jpg

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

http://img228.imageshack.us/img228/2976/outputq.jpg

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

http://img697.imageshack.us/img697/7049/output2.jpg

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:

http://rapidshare.com/files/397417795/TESST.DSN.html

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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From: mike742 on 10 Jun 2010 15:24
> 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:
>
> http://img571.imageshack.us/img571/6449/fig4.jpg

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...
From: electro_1 on 11 Jun 2010 10:37
Thank you so much mike!

Cheers

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