I'm hvaing trouble with my circuit, it's suppose to be a load switch to turn on a wifi module. However it's not working as intended. The idea is to set WIFI_CTRL to high to turn on WIFI_ENABLE.

The compnents are:

Q3=TSM250N02CX TSM250N02CX

Q4=DMP1045UQ DMP1045UQ

I tried reducing the resistance of R10 to 1K and even 100 Ohm for a stronger pull-up but still WIFI_Enable is just down to 1.5V.

Can anyone pinpoint my issue, or recommend suitable SOT-23 replacements ? Circuit


Your P channel MOSFET is upside down. And now the P-channel body diode is always in forward biased and turn-on your WIFI_ENABLE regardless Q4 state.

P-MOSFET body diode

P channel MOSFET source need to be connected to VCC3


You are missing a pull-down resistor on the gate terminal of Q4. Without this resistor small charges at the gate can keep the MOSFET turned on.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.