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I want to use a small slide switch to turn my circuit on and off so that the circuit draws no/very little power when off. The circuit will only draw a maximum of approx. 500mA @ 5V when on, but to my surprise the switch I want to use is not rated to this. So I decided to use an N-channel MOSFET to switch my circuit on and off. Part number for the MOSFET is DMN3404L-7. A bit overkill, I know. N-channel MOSFET as a power switch

Header P1 is the power supply header for the entire circuit.

I am wondering if this is a proper implementation of an N-channel MOSFET. In particular, is there a good reason why I should not connect the drain port to common ground as shown? Also would a P-channel MOSFET on the high side be better suited for this?

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  • \$\begingroup\$ Is this entire setup for that single LED, or is there more of the circuit you haven't shown? \$\endgroup\$ – Reinderien May 22 '18 at 16:28
  • \$\begingroup\$ Also, it seems you're using the symbol for a thermistor instead of a fuse. \$\endgroup\$ – Reinderien May 22 '18 at 16:30
  • \$\begingroup\$ @Reinderien There is more of the circuit that is not shown. It figured it wasn't relevant so I didn't include it. F1 is a PTC (resettable fuse). Maybe I got the designator (or symbol) wrong :S \$\endgroup\$ – Ndnes May 22 '18 at 16:38
  • \$\begingroup\$ At the risk of stating the obvious: why not just use a better switch? \$\endgroup\$ – Reinderien May 22 '18 at 16:40
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    \$\begingroup\$ Depending on your load and what it might need to interface with and how your power supply 0 volts might interact with other circuits a P type MOSFET may be the only sensible route. \$\endgroup\$ – Andy aka May 22 '18 at 18:08
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Yes that should work just fine. However you need to be careful with the other side of your circuit because if it becomes grounded it will bypass the N-Channel MOSFET. This is why a P-Channel switching the VCC is usually preferred.

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  • \$\begingroup\$ The reason why I'm using N Channel is because the same component is used in other parts of my circuit, and I want to keep the unique part numbers low. \$\endgroup\$ – Ndnes May 22 '18 at 21:04

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