Electronics Forum / Basics / July 2006

hello,

I was wondering how much voltage should we measure in the gate of a
P-channel power MOSFET. I ask this because I am trying to repair a
Philips monitor. I found out that the B+ going to the collector of HOT
connected on the drain of a power MOSFET (IRF 9620). The low voltage
power supply works fine. I can measure dc voltage on the source
terminal of the MOSFET but there is no voltage present on the drain. So
there is no HOT collector voltage. Now measure the gate dc voltage and
the dc gate voltage I think is too high (same voltage as with the
source). Gate is connected through a crystal diode and a 22k resistor.
Are these passive components do not provide any voltage drop to the
gate? Can anyone give me some explanation about this and how P-channel
mosfet works in general. Also what is gate drive?

thanks in advance for explanation and patience.

ian