FET gm

Discussion in 'Homework Help' started by Steve1992, Jun 16, 2011.

  1. Steve1992

    Thread Starter Senior Member

    Apr 7, 2006
    100
    0
    Hi,

    Ive put a basic MOSFET voltage amplifier in a circuit simulator.

    Measured values from circuit simulator:
    Vgs = 2.52V
    Id = 900uA

    Calculated, gm = 900uA / 2.52V = 357uS

    But the circuit simulator shows gm as 6mA/V

    :confused:
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Gm is not I/V, where I and V are DC measurements. Gm is i/v, where i and v are small-signal measurements. Another way of putting it: Gm=dI/dV, which is the rate of change of current as a function of voltage.
    Gm will change as the operating point changes.
     
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