P-Channel MOSFET always on

Thread Starter

AAnkur

Joined Jan 29, 2015
8
Hello

Hello
I am using a MOSFET driver circuit with SI2303 as p-channel mosfet and SI2302 as n-channel mosfet.
I have given control signal (of 5V) on the gate of n-channel mosfet to turn-on and off the p-channel mosfet.

However, the p-channel mosfet is not getting off and I am constantly finding voltage on Output (marked as Point-A).
Please let me know what is the problem in this circuit.
Thanks

MOSFET_AAnkur.png
 

DickCappels

Joined Aug 21, 2008
8,705
Even when a MOSFET is not driven on there is some leakage current between the source and drain. Do you have a load from the drain of the P-channel to ground? If not, you might want to add a load or dummy load resistor to ground and measure again.

1652691686418.png

The drain current should be only a few microamps - enough to show up on a DVM. A 1k resistor from the P-channel drain to ground should show zero to a few millivolts across the resistor
 

LowQCab

Joined Nov 6, 2012
2,043
A 100k Resistor on the P-FET might be too much Resistance to completely turn it off,
it will certainly make it Switch slowly.
Are You trying to conserve Battery-Power ?
Try making the Resistors ~10-times smaller.
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