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MOSFET as PWR/GND DPST Switch

Electrical Engineering Asked by marksy95 on November 25, 2021

I have started trying to replace relays in my (12V) electrical circuits with MOSFETs. I have somewhat limited experience with MOSFETs, but I think I’m starting to understand it more.

I’ve drawn a circuit that I believe would work as a replacement for a DPST relay. However, of the 2 poles that are switching at the output, one is power and one is ground. If these were ideal switches, I would have no reservations about this, but these being actual devices I know the response is not immediate.

  1. Is my circuit design correct? I’m just getting used to using MOSFETs and could’ve made a mistake. The intended functionality is for the output to be +12V normally, and GND when the 12V switch is closed.

  2. Do I need to worry about the potential momentary short created when the 12V switch is closed? If so, what can be done to avoid the short?

DPST MOSFET Circuit

This is the relay it is meant to replace:
DPST Relay to be Replaced

[update] The circuit initially included a P-ch depletion FET, which (pretty much) doesn’t exist. This has been replaced with an N-ch depletion FET and an inverter (P-ch enhancement) in the following updated schematic.

Updated DPST MOSFET Circuit

The same questions still apply.

  1. Is my circuit design correct? I’m just getting used to using MOSFETs and could’ve made a mistake. The intended functionality is for the output to be +12V normally, and GND when the 12V switch is closed.

  2. Do I need to worry about the potential momentary short created when the 12V switch is closed? If so, what can be done to avoid the short?

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