Help Figure Out This Circuit?, series multivibrator

[ACHIEVEIT]

At first i tried 2k but again it was just straight line, so i tried 1k5 and 1μF caps and the result was the following. Blue line is the collector of the npn and green line is the emitter of the npn. You can't see it very clearly but in the part that seems like exponential fall for the green line, the two lines coexist (one on top of the other)

 

[Roff]

I am aware what the effect of saturation of transistors will have on β, the suggestion of a 2K7 resistor test, was to make the discharge paths the same, in order to produce an approx equal mark space ratio so that the OP could observe the effect of the diode in/out.

It would be then an easy task to increase the values of the two timing caps to give a freq required by the OP.

Can you say what the mark/space result was with < 2K2 and the *10 caps, I dont use a circuit simulator.

With 100nF caps, 470k timing resistors, and 2.2k between the emitters, the period was 2.5ms, and the discharge time was 200us. I am using 2N3904/2N3906.

 

[ericgibbs]

With 100nF caps, 470k timing resistors, and 2.2k between the emitters, the period was 2.5ms, and the discharge time was 200us. I am using 2N3904/2N3906.

Many thanks, I suppose I should consider using a Circuit Sim, can you recommend one.?

 

[Roff]

Many thanks, I suppose I should consider using a Circuit Sim, can you recommend one.?

The only one I use is LTspice IV , which is totally free and uncastrated (as opposed to demo and student versions of some other simulators). There is a great **broken link removed** if you need it. There are also some here on the forum (including me) who can help.
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[ACHIEVEIT]

I only knew of Orcad Capture/PSpice because that's the one they taught us at the university. But i installed LTSpice (because Ron said the circuit worked in his ) and it is pretty straightforward with a good library of components. So, i would recommend it as well

 

[ericgibbs]

I only knew of Orcad Capture/PSpice because that's the one they taught us at the university. But i installed LTSpice (because Ron said the circuit worked in his ) and it is pretty straightforward with a good library of components. So, i would recommend it as well

hi,
Just had a quick run thru LTSpice, looks a fairly easy program to learn and use.

I normally design circuits using conventional methods which I find easy to do,
but we get so many posters asking for help in sorting out designs which have been done on simulators.

So it will speed up checking if I can load the posters sim circuit directly into a sim program the poster is using,
in order that I can check their designs.

At what stage are you now at with the original posted question.??

 

[Roff]

hi,
Just had a quick run thru LTSpice, looks a fairly easy program to learn and use.

I normally design circuits using conventional methods which I find easy to do,
but we get so many posters asking for help in sorting out designs which have been done on simulators.

So it will speed up checking if I can load the posters sim circuit directly into a sim program the poster is using,
in order that I can check their designs.

At what stage are you now at with the original posted question.??

I'm in a holding pattern.
Attached is the "executable" for the similation. It will run on LTspice. If you associate .ASC with LTspice, it should run when you double-click on it.