g_m of MOSFET is controlled by

Solution (By Examveda Team)

The correct answer is Option A: gate-source voltage.
Let's break down why:
gm (transconductance) of a MOSFET tells us how much the drain current (Id) changes for a small change in the gate-source voltage (Vgs).
Think of it like this: If you slightly adjust the voltage on the gate (Vgs), how much does the current flowing through the MOSFET from drain to source (Id) change?

Option A: gate-source voltage (Vgs) - This is the primary way to control gm. A higher Vgs generally leads to a higher gm.

Option B: drain-source voltage (Vds) - While Vds *does* influence the drain current, and therefore indirectly *can* affect gm, it's not the primary control. gm is *defined* by the relationship between gate voltage and drain current. Vds mainly affects the *saturation* region of operation, but the *control* is still largely through the gate.

Option C: drain current (Id) - gm and Id are related, but Id doesn't directly *control* gm. Instead, gm is a *property* that describes how Id responds to changes in Vgs.

Option D: gate current (Ig) - In a MOSFET, the gate current is ideally very, very small (close to zero). Therefore, it does not control gm. The gate is insulated.

In simpler terms: The gate-source voltage (Vgs) is like the accelerator pedal in a car. It directly controls how much current (Id) flows through the MOSFET. gm is a measure of how sensitive the current flow is to changes in the accelerator pedal.