Uncommon mosfet usage

Question

Occasionally I am faced with a problem where I am faced with a device that needs two of it's inputs to be shorted together for something to activate (Think smoke machine or gate motor).

This is the circuit I have been using:

^{simulate this circuit – Schematic created using CircuitLab}

The idea is that the resistance of the mosfet goes down when a signal is applied which simulates the short circuit. My concern is that this feels very unconventional.

Is this an acceptable method of doing this? are there more professional methods?

note: it isn't as simple as sending a '0' signal. That often isn't how these systems work.

thanks.

Answer 1

The answer is, it depends.

If the gate drive is floating this will work fine, though note it has a polarity due to the intrinsic diode in the MOSFET.

^{simulate this circuit – Schematic created using CircuitLab}

This however.. will not.

^{simulate this circuit}

If you need to do multiples, you would need a common ground everywhere.

^{simulate this circuit}

A better method would be to use a relay or better still an opto-coupled MOSFET.

The latter is also bi-polar due to the back-to-back MOSFETS which block the diodes.