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I'm designing a small circuit with 3 pins: PIN1, PIN2, and CONTROL.

I want the circuit to have PIN1 and PIN2 connected if CONTROL outputs a high voltage, and have PIN1 and PIN2 disconnected if CONTROL outputs a low voltage.

By 'connected' I mean that I want to approximate a manual switch as much as possible--so when the voltage at CONTROL goes from low to high, it works as though I had physically shorted PIN1 and PIN2.

The only reason I'm not actually using a manual switch is that I need the connection & disconnection to happen at a very specific time, which I can accomplish by toggling the control voltage.

Here is the circuit I'm planning to use, with two generic N-type MOSFETs:

In the rest of the circuit, PIN1 connects to a voltage regulator and PIN2 connects to the voltage its trying to regulate.

My goal with the circuit is to have the voltage regulator regulating the PIN2 voltage when CONTROL is set high, and have the PIN2 voltage be unregulated when CONTROL is set low. Does the circuit I proposed do that correctly, and if it doesn't, what would be a better alternative?

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    \$\begingroup\$ Pin 1 and Pin 2 are always connected by the body diodes. If the voltage between them reaches 0.6V, these will conduct. \$\endgroup\$
    – user16324
    Commented Aug 7, 2021 at 20:08
  • \$\begingroup\$ Think about what effect the parasitic body diodes in the mosfets will have. \$\endgroup\$
    – Dean Franks
    Commented Aug 7, 2021 at 20:09
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    \$\begingroup\$ Draw a schematics of the regulator with a mechanical switch and CONTROL signal, then we'll find a best solution for ya. \$\endgroup\$
    – Marko Buršič
    Commented Aug 7, 2021 at 20:33

1 Answer 1

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You do have to place MOSFETs in series and drive them with a gate driver that is floating potential - this implies the use of an isolated DC/DC converter.

schematic

simulate this circuit – Schematic created using CircuitLab

Alternatively you could use a photovoltaic MOSFET gate driver.

enter image description here

There are also solid state relays (SSR) IC VO14642:

enter image description here

It all depends on swtching speed, load current, voltage. Parameters that you didn't specify in your question.

Yet another possibilty is to use analog switches:

enter image description here

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  • \$\begingroup\$ Most analog switches have ON resistances of several ohms making them unsuitable for switching power; the OP forgot to mention the application, but they should bear this in mind. \$\endgroup\$
    – user16324
    Commented Aug 8, 2021 at 21:39

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