Terminating unused FETS

Discussion in 'General Electronics Chat' started by Brian Robson, Jan 5, 2015.

  1. Brian Robson

    Thread Starter New Member

    Nov 13, 2014
    I know that unused op-amps that come in multiple packages should be terminated or they could potentially produce noise. Is it recommended to terminate FETs in a similar way?
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    More than recommended, I would say mandatory. Without connecting the source and gate via a resistor the transistor will open if the gate is left unconnected, either fully or partially, and will be very susceptible to EMI. If it opens partially and is used as a high power switch it may also overheat and get destroyed.
  3. #12


    Nov 30, 2010
    Yes. You should have the gates connected to the sources. FET gates have such high impedance that static electricity fields that you wouldn't even notice can turn them on, where they can drift in some stage of conduction for hours. Conduct to what? They aren't connected to anything.

    Yes they are. They must be in a chip with several transistors or you wouldn't have extras. Play it safe. Put a leash on those extra dogs.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Even better, tie the gate to drain, and connect source to Gnd.
  5. Brian Robson

    Thread Starter New Member

    Nov 13, 2014
    Great, thanks for the feedback. Source grounded and gate tied to drain.