Re: gEDA-user: Multivibrator Simulation

["A.Burinskiy" <alexbour@xxxxxxxxx>]

Hi Michael,

This circuit has stable state when both Q1,2 are in saturation. This 
circuit has trouble to oscillate in real life. It may starts only during 
powerup due to asymmetry in the branches. But in simulator all 
components have perfect match. In short, that is not simulator problem, 
it is circuit problem. You may try to use "kick start" - provide short 
but powerful enough kick start current into one of the base of Q1 or Q2. 
But best way will be having some negative feedback to stabilize Q1,2 
around operating point.

Thanks,
Alex.


On 06/23/2009 08:45 AM, Michael B Allen wrote:
> Hi,
>
> I'm trying to run a simple multivibrator simulation but both SPICE and
> GNU-Cap do not yield anything that even oscillates. Here is the
> circuit:
>
>    http://207.192.69.113/~miallen/mv_1.pdf
>
> Is there anything wrong with this? Is there any trick to getting
> something like this to work?
>
> Also, ultimately I want to build this circuit for the purpose of
> testing and calibrating a buffer circuit for a sound card
> oscilloscope. Can someone suggest how I might modify the circuit to:
>
>    1. Control the amplitude so that I can use the square wave as a
> reference voltage to calibrate the oscilloscope software. Perhaps if I
> use a diode I know when I reach 0.6 V? Or can I just measure the
> square wave with a volt meter and compute the DC levels of the square
> wave horizontals?
>
>    2. Make the primary frequency adjustable between 20 Hz and 20 KHz
>
> Note that I'm not an EE and I'm using gspiceui. I'm just trying to
> validate the theory before I start messing around with wires and such.
>
> Mike
>
>
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>
>    



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