BJT Flip Flop - problem or confusion?

[juz_ad]

Trying to work out if I have a problem with my flip flop circuit sim or if the problem is with my understanding of the expected behaviour of this circuit?

Simulating a BJT Flip Flop. Each input receives a pulse - going to GND - at different intervals.

I would have expected that for each pulse received on either input, the output would have changed state from High to Low and maintained that state until another pulse was received at either input. This isn't the behaviour I'm getting.

I've tried the same with positive-going pulses - similar results. Top image shows pulses, bottom shows FF output.

What's wrong? Thanks!

 

[chuckey]

Its your actual flip flop signal its holding the bases to earth potential, when they should be biased to +.6V by the current flowing down from the opposite collector which should be high.
Remove one signal. Connect each base to earth via a 10 K (gets rid of any leakage current), AC couple the flip flop signal back to one base. Monitor big squarewave at a collector. Go out and have a beer.
Frank

 

[dick_freebird]

Holy '80s, Boy Wonder! Or '70s; already fading technology
when I started working in it, back then.

The drive pulses in practicality would be from the collector
of another common-emitter NPN, a unidirectional current
(sink) pulse to GND. Voltage mode drive is unrealistic and
un-useful. Try modeling the drive as ipulse with normal
DC current and baseline transient current being 0, and your
set / reset pulses being something like 12mA (this depends
mightily on VIN and resistor tempco).

I'm not sure I like the 10K resistors, we never used that
style back in the day of the mighty bipolar 1Kx1 SRAM.
Just simple cross coupling B-C, C-B.

You must respect the saturation recovery time, which
some of your S/R pulse spacings seem to be crowding
as I read it.

 

[crutschow]

What you have is commonly referred to as a latch. It does not alternate states when the same input is pulsed more than once as a toggle Flip Flop does.
When Clk1 is grounded, OUT2 should go high. Further Ckl1 pulses will have no effect.
When Ckl2 is grounded, OUT1 should go high. Further Ckl2 pulses will have no effect.