Answer to Question #143239 in Electrical Engineering for NAVANIT KRISHNA

Question

Explain the working of N channel Enhancement MOSFET with all necessary diagrams? What is the significance of the gate-source voltage?

Answer 1

Source: https://learningaboutelectronics.com/Articles/N-Channel-MOSFETs

A N-Channel MOSFET is a type of MOSFET in which the channel of the MOSFET is composed of a majority of electrons as current carriers. When the MOSFET is activated and is on, the majority of the current flowing are electrons moving through the channel.

This is in contrast to the other type of MOSFET, which are P-Channel MOSFETs, in which the majority of current carriers are holes.

Before, we go over the construction of N-Channel MOSFETs, we must go over the 2 types that exist. There are 2 types of N-Channel MOSFETs, enhancement-type MOSFETs and depletion-type MOSFETs.

A depletion-type MOSFET is normally on (maximum current flows from drain to source) when no difference in voltage exists betweeen the gate and source terminals. However, if a voltage is applied to its gate lead, the drain-source channel becomes more resistive, until the gate voltage is so high, the transistor completely shuts off. An enhancement-type MOSFET is the opposite. It is normally off when the gate-source voltage is 0 (VGS=0). However, if a voltage is applied to its gate lead, the drain-source channel becomes less resistive.

In this article, we will go over how both N-Channel enhancement-type and depletion-type are constructed and operate.

How N-Channel MOSFETs Are Constructed Internally

An N-Channel MOSFET is made up of an N channel, which is a channel composed of a majority of electron current carriers. The gate terminals are made up of P material. Depending on the voltage quantity and type (negative or positive) determines how the transistor operates whether it turns on or off.

How an N-Channel Enhancement type MOSFET Works

How to Turn on a N-Channel Enhancement type MOSFET

To turn on a N-Channel Enhancement-type MOSFET, apply a sufficient positive voltage VDD to the drain of the transistor and a sufficient positive voltage to the gate of the transistor. This will allow a current to flow through the drain-source channel.

So with a sufficient positive voltage, VDD, and sufficient positive voltage applied to the gate, the N-Channel Enhancement-type MOSFET is fully functional and is in the 'ON' operation.

How to Turn Off an N-Channel Enhancement type MOSFET

To turn off an N-channel Enhancement MOSFET, there are 2 steps you can take. You can either cut off the bias positive voltage, VDD, that powers the drain. Or you can turn off the positive voltage going to the gate of the transistor.

How a N-Channel Depletion-type MOSFET Works

The gate voltage helps control the system.