Some food for thought. I used to do diode measurements and recall this: di/dt. Specs are written at a specific current. The effective transition directly relates to the impedance. I believe di/dt is ignored. Physics Rules. . -Bill . ----- Original Message ----- From: "Jack Smith" To: "[EE] Microcontroller discussion list - Public." Sent: Saturday, December 29, 2007 4:12 PM Subject: Diode Turn-on Time (was MOSFET) (Sorry - sent originally without the [EE] tag.) After reading the discussion concerning protecting MOSFETs from inductive spikes with diodes, I've just finished turn-on and turn-off time measurements for four power diodes; two 1N400x type, one high speed silicon and one Schottky diode. Discussion and 'scope photos at http://www.cliftonlaboratories.com/diode_turn-on_time.htm I see the expected difference in reverse recovery time, but all four diodes have very short transitions from reverse to forward bias. Perhaps I'm misunderstanding what is going on, or perhaps there's an issue with my test setup, but all four diodes look like they transition in a few nanoseconds. Certainly well under 100 ns. I didn't drag my 400 MHz digital 'scope over to the other side of the shop for the data, so it's taken with a 100 MHz analog scope, but I don't think that's the reason. To me, all four diodes look as if they would provide more than fast enough transition from reverse to forward bias conditions. What am I doing wrong here? Jack -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist