P-Channel Enhancement MOSFET. Products (2,900) Datasheets (2,283) Images (407) Newest Products -Results: 2,900. Smart Filtering As you select one or more parametric filters below, Smart Filtering will instantly disable any unselected values that would cause no results to be found. Its maximum power dissipation is 75000 mW. This product comes in rail packaging to keep individual parts separated and protected. This MOSFET transistor has a minimum operating temperature of -55 °C and a maximum of 150 °C. This P channel MOSFET transistor operates in enhancement mode. The P-channel MOSFETs are simply called as PMOS. The symbols for P-channel MOSFET are as given below. Now, let us go through the constructional details of an N-channel MOSFET. Usually an NChannel MOSFET is considered for explanation as this one is mostly used.
In this tutorial, we will have a brief introduction to MOSFET i.e., the Metal Oxide Semiconductor Field Effect Transistor. We will learn about different types of MOSFET (Enhancement and Depletion), its internal structure, an example circuit using MOSFET as a Switch and a few common applications.
Transistors, the invention that changed the World. They are semiconductor devices that act as either an electrically controlled switch or a signal amplifier. Transistors come a variety of shapes, sizes and designs but essentially, all transistors fall under two major families. They are:
- Bipolar Junction Transistors or BJT
- Field Effect Transistors or FET
To learn more about a basics of transistor and its history, read the Introduction to Transistors tutorial.
There are two main differences between BJT and FET. The first difference is that in BJT, both the majority and minority charge carriers are responsible for current conduction whereas in FETs, only the majority charge carriers are involved.
The other and very important difference is that a BJT is essentially a current controlled device meaning the current at the base of the transistor determines the amount of current flowing between collector and emitter. In case of a FET, the voltage at the Gate (a terminal in FET equivalent to Base in BJT) determines the current flow between the other two terminals.
FETs are again divided into two types:
- Junction Field Effect Transistor or JFET
- Metal Oxide Semiconductor Field Effect Transistor or MOSFET
Let us focus on MOSFET in this tutorial.
Metal Oxide Semiconductor FET
The Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is one type of FET transistor. In these transistors, the gate terminal is electrically insulated from the current carrying channel so that it is also called as Insulated Gate FET (IG-FET). Due to the insulation between gate and source terminals, the input resistance of MOSFET may be very high such (usually in the order of 1014 ohms.
Like JFET, the MOSFET also acts as a voltage controlled resistor when no current flows into the gate terminal. The small voltage at the gate terminal controls the current flow through the channel between the source and drain terminals. In present days, the MOSFET transistors are mostly used in the electronic circuit applications instead of the JFET.
MOSFETs also have three terminals, namely Drain (D), Source (S) and Gate (G) and also one more (optional) terminal called substrate or Body (B). MOSFETs are also available in both types, N-channel (NMOS) and P-channel (PMOS). MOSFETs are basically classified in to two forms. They are:
- Depletion Type
- Enhancement Type
- Channel Construction of MOSFET
The depletion type MOSFET transistor is equivalent to a “normally closed” switch. The depletion type of transistors requires gate – source voltage (VGS) to switch OFF the device.
The symbols for depletion mode of MOSFETs in both N-channel and P-channel types are shown above. In the above symbols, we can observe that the fourth terminal (substrate) is connected to the ground, but in discrete MOSFETs it is connected to source terminal. The continuous thick line connected between the drain and source terminal represents the depletion type. The arrow symbol indicates the type of channel, such as N-channel or P-channel.
In this type of MOSFETs a thin layer of silicon is deposited below the gate terminal. The depletion mode MOSFET transistors are generally ON at zero gate-source voltage (VGS). The conductivity of the channel in depletion MOSFETs is less compared to the enhancement type of MOSFETs.
The Enhancement mode MOSFET is equivalent to “Normally Open” switch and these types of transistors require a gate-source voltage to switch ON the device. The symbols of both N-channel and P-channel enhancement mode MOSFETs are shown below.
Here, we can observe that a broken line is connected between the source and drain, which represents the enhancement mode type. In enhancement mode MOSFETs, the conductivity increases by increasing the oxide layer, which adds the carriers to the channel.
Generally, this oxide layer is called as ‘Inversion layer’. The channel is formed between the drain and source in the opposite type to the substrate, such as N-channel is made with a P-type substrate and P-channel is made with an N-type substrate. The conductivity of the channel due to electrons or holes depends on N-type or P-type channel respectively.
Structure of MOSFET
- The basic structure of the MOSFET is shown in the above figure. The construction of the MOSFET is very different when compared to the construction of the JFET. In both enhancement and depletion modes of MOSFETs, an electric field is produced by gate voltage, which changes the flow charge carriers, such as electrons for N-channel and holes for P-channel.
Here, we can observe that the gate terminal is situated on top of thin metal oxide insulated layer and two N-type regions are used below the drain and source terminals.
In the above MOSFET structure, the channel between drain and source is an N-type, which is formed opposite to the P-type substrate. It is easy to bias the MOSFET gate terminal for the polarities of either positive (+ve) or negative (-ve).
If there is no bias at the gate terminal, then the MOSFET is generally in non-conducting state so that these MOSFETs are used to make switches and logic gates. Both the depletion and enhancement modes of MOSFETs are available in N-channel and P-channel types.
The depletion mode MOSFETs are generally known as ‘Switched ON’ devices, because these transistors are generally closed when there is no bias voltage at the gate terminal. If the gate voltage increases in positive, then the channel width increases in depletion mode.
As a result the drain current ID through the channel increases. If the applied gate voltage more negative, then the channel width is very less and MOSFET may enter into the cutoff region. The depletion mode MOSFET is a rarely used type of transistor in the electronic circuits.
The following graph shows the Characteristic Curve of Depletion Mode MOSFET.
The V-I characteristics of the depletion mode MOSFET transistor are given above. This characteristic mainly gives the relationship between drain- source voltage (VDS) and drain current (ID). The small voltage at the gate controls the current flow through the channel.
The channel between drain and source acts as a good conductor with zero bias voltage at gate terminal. The channel width and drain current increases if the gate voltage is positive and these two (channel width and drain current) decreases if the gate voltage is negative.
The Enhancement mode MOSFET is commonly used type of transistor. This type of MOSFET is equivalent to normally-open switch because it does not conduct when the gate voltage is zero. If the positive voltage (+VGS) is applied to the N-channel gate terminal, then the channel conducts and the drain current flows through the channel.
If this bias voltage increases to more positive then channel width and drain current through the channel increases to some more. But if the bias voltage is zero or negative (-VGS) then the transistor may switch OFF and the channel is in non-conductive state. So now we can say that the gate voltage of enhancement mode MOSFET enhances the channel.
Enhancement mode MOSFET transistors are mostly used as switches in electronic circuits because of their low ON resistance and high OFF resistance and also because of their high gate resistance. These transistors are used to make logic gates and in power switching circuits, such as CMOS gates, which have both NMOS and PMOS Transistors.
The V-I characteristics of enhancement mode MOSFET are shown above which gives the relationship between the drain current (ID) and the drain-source voltage (VDS). From the above figure we observed the behavior of an enhancement MOSFET in different regions, such as ohmic, saturation and cut-off regions.
MOSFET transistors are made with different semiconductor materials. These MOSFETs have the ability to operate in both conductive and non-conductive modes depending on the bias voltage at the input. This ability of MOSFET makes it to use in switching and amplification.
N-Channel MOSFET Amplifier
When compared to BJTs, MOSFETs have very low transconductance, which means the voltage gain will not be large. Hence, MOSFETs (for that matter, all FETs) are generally not used in amplifier circuits.
But, none the less, let us see a single-stage ‘class A’ amplifier circuit using N-Channel Enhancement MOSFET. The N-channel enhancement mode MOSFET with common source configuration is the mainly used type of amplifier circuit than others. The depletion mode MOSFET amplifiers are very similar to the JFET amplifiers.
The input resistance of the MOSFET is controlled by the gate bias resistance which is generated by the input resistors. The output signal of this amplifier circuit is inverted because when the gate voltage (VG) is high the transistor is switched ON and when the voltage (VG) is low then the transistor is switched OFF.
The general MOSFET amplifier with common source configuration is shown above. This is an amplifier of class A mode. Here the voltage divider network is formed by the input resistors R1 and R2 and the input resistance for the AC signal is given as Rin = RG = 1MΩ.
The equations to calculate the gate voltage and drain current for the above amplifier circuit are given below.
VG = (R2 / (R1 + R2))*VDD
ID = VS/ RS
VG = gate voltage
VS = input source voltage
VDD = supply voltage at drain
RS = source resistance
R1 & R2 = input resistors
The different regions in which the MOSFET operates in their total operation are discussed below.
Cut-off Region: If the gate-source voltage is less than the threshold voltage then we say that the transistor is operating in the cut-off region (i.e. fully OFF). In this region drain current is zero and the transistor acts as an open circuit.
VGS < VTH => IDS = 0
Ohmic (Linear) Region: If the gate voltage is greater than threshold voltage and the drain-source voltage lies between VTH and (VGS – VTH) then we say that the transistor is in linear region and at this state the transistor acts as a variable resistor.
VGS > VTH and VTH < VDS < (VGSVGS – VTH) => MOSFET acts as a variable Resistor
Saturation Region: In this region the gate voltage is much greater than threshold voltage and the drain current is at its maximum value and the transistor is in fully ON state. In this region the transistor acts as a closed circuit.VGS >> VTH and (VGS – VTH) < VDS < 2(VGS – VTH) => IDS = Maximum
The gate voltage at which the transistor ON and starts the current flow through the channel is called threshold voltage. This threshold voltage value range for N-channel devices is in between 0.5V to 0.7V and for P-channel devices is in between -0.5V to -0.8V.
The behavior of a MOSFET transistor in depletion and enhancement modes depending on the gate voltage is summarized as follows.
- MOSFETs are used in digital integrated circuits, such as microprocessors.
- Used in calculators.
- Used in memories and in logic CMOS gates.
- Used as analog switches.
- Used as amplifiers.
- Used in the applications of power electronics and switch mode power supplies.
- MOSFETs are used as oscillators in radio systems.
- Used in automobile sound systems and in sound reinforcement systems.
A complete beginner’s guide to introduction of MOSFET. You learned the structure of a MOSFET, different types of MOSFET, their circuit symbols, an example circuit using a MOSFET to control an LED and also few areas of applications.
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 ofcurrent 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 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
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.
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.
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.
P Channel Enhancement Mosfet As A Switch
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.
P Channel Enhancement Power Mosfet Used For
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.
How to Build a P-Channel MOSFET Switch Circuit
N-Channel MOSFET Basics
N Channel JFET Basics
P Channel JFET Basics
Types of Transistors