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.
- N Channel Mosfet Tutorial
- Difference Between N Channel And P Channel Mosfets
- N Channel Fet
- P Channel Enhancement Mode Mosfet
This is in contrast to the other type of MOSFET, which are N-Channel MOSFETs, in which the majority ofcurrent carriers are electrons.
Using a p-channel MOSFET may place some severe restraints on the gate drive, since the gate must be close to V DD (Figure 1b). To return gate control to a more acceptable logic format, add an n-channel MOSFET (Figure 3). Using an n-channel MOSFET in this way simplifies the gate drive for a high-voltage, high-side, p-channel MOSFET.
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.
- N and P-Channel Enhancement Mode Power MOSFET Description The NCE603S uses advanced trench technology to provide excellent RDS(ON) and low gate charge. The complementary MOSFETs may be used to form a level shifted high side switch, and for a host of other applications. General Features N-Channel VDS = 60V,ID =6.3A RDS(ON).
- MOSFET N-Channel, P-Channel Dual MOSFET Products (341) Datasheets (291).
A depletion-type MOSFET is normally on (maximum current flows from source to drain) when no differencein 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 becomesless 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
N Channel Mosfet Tutorial
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.
Difference Between N Channel And P Channel Mosfets
How to Turn Off a P-Channel Enhancement Type MOSFET
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 voltagegoing to the gate of the transistor.
N Channel Fet
How a P-Channel Depletion-type MOSFET Works
How to Turn on a P-Channel Depletion Type MOSFET
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.
How to Turn Off a P-Channel Depletion Type MOSFET
To turn off a P-channel MOSFET, there are 2 steps you can take. You can either cut off the bias positivevoltage, VDD, that powers the drain. Or you can apply a negative voltage to the gate. When a negativevoltage 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.
P Channel Enhancement Mode Mosfet
How to Build a P-Channel MOSFET Switch Circuit
N-Channel MOSFET Basics
N Channel JFET Basics
P Channel JFET Basics
Types of Transistors
Comparison of N Channel and P Channel MOSFETs
- The P-channel enhancement MOSFETs were very popular, because it was much easier and cheaper to produce than the N channel device.
But now a days these difficulties have overcome and mass production of N-channel MOSFETs becomes easier.
Thus the N-MOSFETS have replaced PMOSs and P-MOSFETs have almost become obsolete.
- The hole mobility is nearly 2.5 times lower than the electron mobility.
Thus a P channel MOSFET occupies a larger area than the N channel MOSFET having the same ID rating.
At normal fields, in silicon,
the hole mobility is 500 cm2/v.sec
the electron mobility is 1300 cm2/v.sec.
Therefore the P-channel ON resistance will be twice that of n-channel MOSFET ON resistance.
- ON resistance means the resistance of the device when ID is maximum for a given VDS. Its value depends upon μ of carriers.
- P-channel device have holes as majority carriers.
- N-channel device have electrons as majority carriers.
- At the same values of ID and VDS, if the ON resistance of P channel device were to be reduced/make equal to that of N-channel device, then the P-channel device must have more than twice the are of N-channel device. Thus the n -channel devices will be smaller is size.
In other words the packing density of N-channel devices is more (R = ρ. l/ A)
- N channel MOSFETs are fast switching devices. The operating speed is limited by RC time constant of the device. The capacitance is proportional to the junction cross sections.
- The N channel MOSFETs are TTL compatible. As the applied gate voltage and drain supply are positive for an n-channel enhancement MOSFET.
- The drain resistance of P channel MOSFET is 3 times higher than that for an identical N-channel MOSFET.
- The N-Channel MOSFET has the higher packing density which makes it faster in switching applications due to the smaller junction areas and lower inherent capacitance.
- The N-channel MOSFET is smaller for the same complexity than P-channel device.
- Due to the positively charged contaminants, the N-channel MOSFET may turn ON prematurely, whereas the P-channel device will not be affected.
The summary of Difference Between N Channel and P Channel MOSFETs are listed in the following table.
|N-Channel MOSFET||P-Channel MOSFET|
|Have higher packing density, leads to small size||Comparatively low packing density.|
|Smaller in size for same complexity||Size will be more.|
|High switching device. (mobility of electrons is high)||Low switching speed. (mobility of holes is low)|
|Low ON resistance||High ON resistance.|
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