I understand how the flip-flop works, but don't understand the exact waveforms of the voltages. 1) How is it possible that the pnp collector voltage gets negative? 2) Do you see how the same voltage first grows a little, then it stops and hesitates at that level, and only after some time it flips up? What is the hesitation caused by? I would expect the voltage going up till it reaches the npn saturation level, and then flipping stright up - without the stop in the middle.
