P-Channel MOSFET Basics
A P-Channel MOSFET is a type of MOSFET in which the channel of the MOSFET is composed of a majority of holes as current carriers. When the MOSFET is activated and is on, the majority of the current flowing are holes moving through the channels.
This is in contrast to the other type of MOSFET, which are N-Channel MOSFETs, in which the majority of current carriers are electrons.
Before, we go over the construction of P-Channel MOSFETs, we must go over the 2 types that exist. There are 2 types of P-Channel MOSFETs, enhancement-type MOSFETs and depletion-type MOSFETs.
A depletion-type MOSFET is normally on (maximum current flows from source to drain) when no difference in voltage exists between 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 0V (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 P-Channel enhancement-type and depletion-type MOSFETs are
constructed and operate.
How P-Channel MOSFETs Are Constructed Internally
An P-Channel MOSFET is made up of a P channel, which is a channel composed of a majority of hole current carriers. The gate terminals are made up of N-type material.
Depending on the voltage quantity and type (negative or positive) determines how the transistor operates and whether it turns on or off.
How a P-Channel Enhancement-type MOSFET Works
How to Turn on a P-Channel Enhancement Type MOSFET
To turn on a P-Channel Enhancement-type MOSFET, apply a positive voltage VS
to the source of the MOSFET and apply a negative voltage to the gate terminal of the
MOSFET (the gate must be sufficiently more negative than the threshold voltage across the drain-source region
(VG So with a sufficient positive voltage, VS, to the source and load, and sufficient negative voltage
applied to the gate, the
P-Channel Enhancement-type MOSFET is fully functional and is in the active 'ON' mode of operation.
To turn off a P-channel enhancement type MOSFET, there are 2 steps you can take. You can either cut off the bias
positive
voltage, VS, that powers the source. Or you can turn off the negative voltage
going to the gate of the transistor.
To turn on a P-Channel Depletion-Type MOSFET, for maximum operation, the gate voltage feeding the gate terminal
should be 0V. With the gate voltage being 0V, the drain current is at is largest value and the transistor is in the active 'ON'
region of conduction.
So, again, to turn on a P channel depletion-type MOSFET, positive voltage is applied to the source of the p-channel MOSFET. So we power the source terminal of the MOSFET with
VS, a positive voltage supply. With a sufficient positive voltage, VS, and no voltage (0V) applied to
the base, the
P-channel Depletion-type MOSFET is in maximum operation and has the largest current.
To turn off a P-channel 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 apply a negative voltage to the gate. When a negative
voltage is applied to the gate, the current is reduced. As the gate voltage, VG,
becomes more negative, the current
lessens until cutoff, which is when then MOSFET is in the 'OFF' condition. This stops a large
source-drain current.
So ,again, as negative voltage is applied to the gate terminal of the P channel depletion-type MOSFET, the MOSFET conducts less and less current
across the source-drain terminal. When the gate voltage reaches a certain negative voltage threshold, it shuts the transistor off. Negative voltage shuts the
transistor off. This is for a depletion-type P-channel MOSFET.
MOSFET transistors are used for both switching and amplifying applications. MOSFETs are perhaps
the most popular transistors used today. Their high input impedance makes them draw very little input current,
they are easy to make, can be made very small, and consume very little power.
Related Resources
How to Build a P-Channel MOSFET Switch Circuit
How to Turn Off a P-Channel Enhancement Type MOSFET
How a P-Channel Depletion-type MOSFET Works
How to Turn on a P-Channel Depletion Type MOSFET
How to Turn Off a P-Channel Depletion Type MOSFET
N-Channel MOSFET Basics
N Channel JFET Basics
P Channel JFET Basics
Types of Transistors