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I'm trying to get a simulation of a standard a stable multivibrator working in circuit lab . This circuit https://www.circuitlab.com/circuit/93yg76/astable-multivibrator/ is supposed to have a period of 1 second but when I run the Time Domain simulation I don't get the expected oscillating current waveforms.

Can anyone help me with what I'm doing wrong?

Thanks, Aaron

Hi,

I also had problems to get my multivibrator working in the simulator.

Now after I added a small capacitor from the collector of one transistor to ground it works with Time Domain simulation. I also had to set "Skip Initial" to yes.

https://www.circuitlab.com/circuit/ubtf3r/amv/

Sven

Thanks, that helped me get a bit further. Still not getting the results I expected though. I think I'll build my physical circuit to compare the simulation results with.

Search CL for:

astable flip flop

startup

initial conditions

:)

Well I found your circuit for the same function and played around with it a little bit. The simulation runs correctly on the circuit I modified from yours (https://www.circuitlab.com/circuit/tx5a3m/signalitys-modded-astable-multivibrator/) but not on the one I created from scratch (https://www.circuitlab.com/circuit/93yg76/astable-multivibrator/) which as best as I can tell is identical. There must be something else I'm missing :(.

Could this be the problem:

R3 = 330k

R4 = 331R ???!!!

:)

Whoops. Thanks. Too long spent staring at the same circuit. Working properly now.

Yeay!

Result!