I have a diode in my circuit with reverse voltage of 100 V and forward voltage of 2 V.

It experiences a reverse voltage of 100 V and immediately the voltage changes to 10 V in forward direction so it becomes conductive. What i am curious to know is how much time does it take for diode to become conductive?

I know there are two parameters "reverse recovery time" and "forward recovery time" . But are they related to this matter ?

My understanding is that recovery time is the time for the internal voltage of diode be made both in forward and reverse direction. So when voltage changes from -100 V to +10 V it takes recovery time for diode to change its internal voltage from 100 V to its breakdown voltage (-2 V). Based on this view, the diode should get in its full conductive state, even in the recovery time since the internal 100 V is in direction of current and does not block it. Is my understanding correct?

  • \$\begingroup\$ Please link the data sheet of the diode and please don't operate it at a reverse voltage equal to its absolute maximum rating. \$\endgroup\$
    – Andy aka
    Dec 2, 2023 at 12:30
  • \$\begingroup\$ What current, and dI/dt? What is the surrounding circuit? How fast is "immediately" really? Please show the waveforms. \$\endgroup\$ Dec 2, 2023 at 13:42

1 Answer 1


For a 1N4007, it should be ~ 200 ps from -100 V to +100 V.
This "forward on" time could change with the direct voltage value used.
Note that I don't use "forward recovery" ... because it is not a "recovery".

Simulated with microcap v12.

But this time can't be compared with the "reverse recovery time" which should be 3.5 us.

enter image description here

  • \$\begingroup\$ I can't speak for Microcap, but no SPICE engine I've seen, has a model of forward recovery; so this isn't surprising. (Recovery in general is a diffusive transport problem, that can only be approximated down to some time scale, beyond which the model becomes invalid; SPICE's reverse recovery model is a single-order approximation, and on similar time scales, forward recovery is generally negligible.) \$\endgroup\$ Dec 2, 2023 at 14:11

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