|
I think I found an EC bug. (Requesting comments.)
The capacitor, BJT, and two resistors make up a monostable multivibrator. It is triggered by a falling edge.
Why then does it also produce a pulse on the rising edge? It doesn't. It produces a pulse AFTER the rising edge due to ringing -- the current through the capacitor goes past zero. This is not necessarily a bug, it could be right for this circuit.
Switching the input of the comparator to the logic source should make no difference. Instead, the ringing is suddenly absent. Why? If, IF, there is any simulateable difference in the output of the comparator, it should be sharper and thus MORE likely to produce ringing.
Slow the simulation down to 10μs/s for more accuracy, and the ringing remains. (It may not look like it because the ringing is -590μA while the positive spike is nearly 60mA, but you can see the blue line dip very slightly.)
Switch to the logic source at 10μs/s and there's more current in the falling edge; 1mA instead of 800μA. There is again no ringing, the maximum current again approaching 60mA but the minimum is only -418nA.
ARGH! adjust the logic source to 25% delay, (to match the cycle of the triangle wave,) and the ringing goes away WHEN THE INPUT COMES FROM THE TRIANGLE WAVE! This is definitely a bug, unless I stumbled on an inherent problem with transient simulation.
|
