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Project Notes

#066 Digital Logic Switch - N-Channel Enhancement FET

Using a small-signal n-channel MOSFET as a switch, with turn-off delay.

Here’s a quick video of the circuit in action:

SwitchNFET demo


N-Channel Enhancement FETs are easy to use as a digital switch:

  • ON when gate-source voltage is much greater than threshold voltage (into saturation region)
  • OFF when gate-source voltage is below threshold voltage (0.8-3V for 2N7000)

This circuit demonstrates the basic switch, with the addition of a turn-off delay.

The turn-off delay is implemented with a simple RC circuit: the R1=220kΩ C1=10μF pair having a time constant of 2.2 seconds.


The Breadboard

The Schematic

The Build

Credits and References

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LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

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