- #1

pc2-brazil

- 205

- 3

## Homework Statement

A specific type of MOSFET has [itex]V_T = -1\ \rm V[/itex]. The MOSFET is in the ON state when [itex]v_{GS} \geq V_T[/itex]. The MOSFET is in the OFF state when [itex]v_{GS} < V_T[/itex].

a) Graph the [itex]i_{DS}[/itex] versus [itex]v_{GS}[/itex] characteristics of this MOSFET.

## Homework Equations

## The Attempt at a Solution

My doubt concerns part a. I will use the switch-resistor (SR) model (the ON state of the MOSFET is modeled as a resistance [itex]R_{ON}[/itex] between the drain and the source). So, the graph of [itex]i_{DS}[/itex] versus [itex]v_{GS}[/itex] would have [itex]i_{DS} = 0[/itex] for all [itex]v_{GS} < V_{T}[/itex].

But what about the case where [itex]v_{GS} \geq v_T[/itex]? The problem is that I don't know how [itex]i_{DS}[/itex] varies as a function of [itex]v_{GS}[/itex].

I know that [itex]i_{DS} = \dfrac{v_{DS}}{R_{ON}}[/itex]; if this value doesn't vary with [itex]v_{GS}[/itex], then, for [itex]v_{GS} \geq v_T[/itex] the graph would have just a horizontal line with y-value [itex]i_{DS} = \dfrac{v_{DS}}{R_{ON}}[/itex].

What am I missing?