Output Characteristics of a MOSFET

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For a MOSFET, the output characteristics is a set of curves - Output drain current against the drain voltage for various values of gate voltage.

Output characteristics

The output characteristics obtained are as below.


The output characteristics – ID vs VDS was simulated on the reference device for various values of VGS at 0.7V, 1V, 2V and 3V.

The output characteristics are obtained by increasing VDS keeping the gate-to-source voltage VGS. It is seen that the maximum current (current in saturation region) increases as the VGS is increased.

For a particular VGS curve, initially, as VDS increases, the current increases rapidly in an exponential manner until the voltage reaches pinch-off value. Thereafter, there is hardly any change in the output current i.e. the current saturates. This is the maximum amount of current from the device.

Output characteristics based on square-law theory

The following equations are used to compute the output characteristics as per square-law theory.
The curves are obtained as below.

Output characteristics based on bulk-charge theory

The following equations are used to compute the output characteristics as per bulk-charge theory.


The curves obtained are as below.

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