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

 

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

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.