source tab vs drain tab transistors

Discussion in 'General Electronics Chat' started by ngal, May 15, 2014.

  1. ngal

    Thread Starter New Member

    May 14, 2014
    Hi all,

    can someone plz help me understand what's the difference between a source tab and a drain tab MOSFET (for example). Does it only have to do with the package of the device and the PCB layout or there is also something else that I need to know?

    Thank you in advance
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    sometimes its so that the drain which is usually at higher voltage is easier to insulate. the source is usually grounded and the tab helps that. even on bipolar rf transistors, its a lot better to have the case or tab connected to the emitter, due to the emitter usually being grounded anyway. this makes a lower impedance ground for the emitter in rf circuits.
    ngal likes this.