MOSFETs - How do you pick 'em?

Discussion in 'General Electronics Chat' started by jbriaris, Apr 18, 2013.

  1. jbriaris

    Thread Starter New Member

    Apr 11, 2013
    With a bewildering variety of MOSFETs available from a myriad of different suppliers, how do you go about picking which one to use in battery-powered applications?

    Leaving cost aside (this is a criteria for any component) what would you say is the most important parameters to consider to prolong battery life? Rds(on), Idss(off), Igss(off) - should one consider more?

    Once you know the characteristics of the MOSFET you want, how do you hone-in on one? Do you use sites like Farnell/Digi-key to make a start, or do you have some superior method you'd like to tell the world?

    Interested for thoughts :rolleyes:
  2. Gibson486

    Active Member

    Jul 20, 2012
    It depends what you are trying to do.....For batteries, you probably want a low level logic mosfet with low Rds to start if you are using it for an on/off switch.

    I find out what my parameters are and then I go to Digikey and filter them out. Then I pick the one that has well over 10,000 in stock. I used to work with a guy who was dead nuts on which manufacturer he used. What a pain that was....
  3. crutschow


    Mar 14, 2008
    As Gibson486 stated, a good place to start is a larger supplier like DigiKey, Mouser, etc. since that way you know what's readily available at what price. From there you need to determine the voltage, current levels, ON resistance and polarity (N or P channel) for your requirements. One significant difference for otherwise similar rated transistors, when used as switches, is the voltage required to turn them fully ON (not the Threshold Voltage which is much smaller). Standard devices require 10V while Logic Level type devices typically require 5V and sometimes only 2.5 or 3V.
  4. jbriaris

    Thread Starter New Member

    Apr 11, 2013
    Great, sounds as though I'm doing it pretty much like everyone else and there is no holy grail solution in the silicon valley :p.

    Yes, crutschow, being pretty new to this electronics stuff I've already learnt about Vgs the hard way!
  5. tindel

    Well-Known Member

    Sep 16, 2012
    I usually start by determining the type of MOSFET I need (logic level, power FET, n or p channel, etc.) Then I check the rated maximum to see if they meet my requirements. Then I start looking into the details of a couple different parts to see if it meets more specific requirements like turn-on/off time, Rds(on), power dissipation, etc.