Q.Describe the output VI characteristics of a power MOSFET.

The output characteristics of a power MOSFET plot drain current $I_D$ against drain-source voltage $V_{DS}$ for a family of gate-source voltages $V_{GS}$, showing cut-off, ohmic and active regions. …

[!TLDR]

Plot $I_D$ vs $V_{DS}$ for increasing $V_{GS}$: cut-off, ohmic (linear, $r_{DS(ON)}$) and active (saturation) regions; the MOSFET is voltage-controlled.

The power MOSFET is a three-terminal voltage-controlled device in which the gate-source voltage $V_{GS}$ controls the current between the drain and source. Its output characteristics show the drain current $I_D$ as a function of the drain-source voltage $V_{DS}$, drawn as a family of curves for increasing values of $V_{GS}$.

The regions are:

• Cut-off region: when $V_{GS}$ is below the threshold voltage $V_{GS(th)}$, no channel is formed and essentially no drain current flows; the MOSFET is OFF.
• Ohmic (linear) region: when $V_{GS}$ is increased beyond $V_{GS(th)}$ and $V_{DS}$ is small, a channel is formed and the drain current is almost proportional to (linear with) $V_{DS}$; in this region the device behaves like a small on-resistance $r_{DS(ON)}$. This is the state used when the MOSFET is ON as a switch.
• Active (saturation) region: at higher $V_{DS}$, the channel pinches off near the drain and the drain current deviates from the linear relation and tends to saturate to an almost constant value for a given $V_{GS}$. …