Transconductance MOSFET 

The Transconductance is the conductance property of the device concerning the input voltage and outputs current, in this post we explain Transconductance MOSFET, so is called the Transconductance of MOSFET which will be gate-source input voltage and drain output current.

Transconductance MOSFET equation

Transconductance is the efficiency of the MOSFET or sensitivity of the MOSFET,


This is the equation of drain current at saturation region, drain current a biasing condition.

 ID = ½ μn . Cox .W/L . (VGS-Vt)2

       = ½ μn . Cox . W/L 2 (VGS – VT)

       = μn . Cox . W/L (VGS-VT)

       = μn. Cox (W/L) Vov

                                Vov = VGS – VT

                                Vov = it is the effective voltage or the over drive voltage, which is the difference between the bias point gate- source voltage and threshold voltage.

       =√2(μn Cox (W/L)ID

      = 2ID/Vov 

    At last, we get an equation of Transconductance MOSFET,

Gm = ΔIout / ΔVin

Transconductance MOSFET graph 

Transconductance MOSFET graph 
Transconductance MOSFET graph

The figure shows the graph of the Transconductance of MOSFET, the graph indicates different values of gate voltage VG and ID current.

  • The Transconductance is the ratio of change in input voltage to change in output current
  • From the graph, it is clear that change in voltage will reflect at the current with representing to this equation 

Gm = ΔIout / ΔVin


  • In this graph (9-7volts)/4mA = ~500, at lower gate voltage. Transconductance is more because the change in ID is less.

Forward Transconductance MOSFET 

The forward Transconductance indicates the signal gain of the, which drain current/ gate voltage is the Transconductance of MOSFET.


Gfs is the indication of forwarding Transconductance

IDS will indicate the high current, the current handling capability can be gathered from the low gate voltage.

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