Due to backemf I seem to be getting a large voltage oscillation as shown in the scope view with channel 2 in blue. It seems to clear 64V there.


This is the circuit.


As shown I tried to put a zener diode 1N5338BG across the resistor going to the gate. The zener has a zener voltage of 5.1V. All it did is clip it down to about 20V as shown in the scope view.


Should it not have clipped it all the way down to 5.1V? Why is this happening?

Does anyone know what the easiest way would be to completely clip all negative voltage, and anything over +3 to 5V? Would a TVS diode work better?

 

To act as a clamp, the Zener would have to be between B and A.

 

To act as a clamp, the Zener would have to be between B and A.

I tried this, same thing, it only clamps it to ~12V. Shouldn't it clamp it to its zener voltage of 5.XV?

 

Where are you putting your scope ground clip?

 

Point A in the schematic.