• Logic Level P Channel Mosfet
• P Channel Power Mosfet
• Mosfet P Channel Vs N Channel
• P Channel Mosfet Depletion

1. P-Channel 1.25-W, 2.5-V MOSFET PRODUCT SUMMARY VDS (V) rDS(on) ( ) ID (A) 20 0.130 @ VGS = -4.5 V -2.3-20 0.190 @ VGS = -2.5 V -1.9 G TO-236 (SOT-23) S D Top View 2 3 1 Si2301DS (A1).Marking Code Ordering Information: Si2301DS-T1 ABSOLUTE MAXIMUM RATINGS (TA = 25 C UNLESS OTHERWISE NOTED) Parameter Symbol Limit Unit Drain-Source Voltage VDS-20 V.
2. The symbols for N-channel MOSFET are as given below. 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.
3. The company, with the new p-channel MOSFET, aims to minimize power losses from conduction and increase efficiency in automotive applications. The latest move is in sync with its persistent focus.

P-CHANNEL ENHANCEMENT MODE MOSFET Product Summary BV DSS R DS(ON) Max Package I D Max T A = +25°C -20V 52mΩ @V GS = -4.5V SOT23 -5.0A 100mΩ @V GS-= -2.5V 3.6A Description This MOSFET is designed to minimize the on-state resistance (R DS(ON)), yet maintain superior switching performance, making it.

Let’s talk about the basics of MOSFET and how to use them. This tutorial is written primarily for non-academic hobbyists, so I will try to simplify the concept and focus more on the practical side of things.

However if you are into how MOSFET work, I will share some useful academic articles and resources at the end of this post. MOSFET has some advantage and disadvantage over BJT, so choose carefully base on your application.

You can buy MOSFET’s for Arduino Projects on Amazon: http://amzn.to/2Gk6ruW

MOSFET stands for metal-oxide semiconductor field-effect transistor. It is a special type of field-effect transistor (FET).

Unlike BJT which is ‘current controlled’, the MOSFET is a voltage controlled device. The MOSFET has “gate“, “Drain” and “Source” terminals instead of a “base”, “collector”, and “emitter” terminals in a bipolar transistor. By applying voltage at the gate, it generates an electrical field to control the current flow through the channel between drain and source, and there is no current flow from the gate into the MOSFET.

A MOSFET may be thought of as a variable resistor, where the Gate-Source voltage difference can control the Drain-Source Resistance. When there is no applying voltage between the Gate-Source , the Drain-Source resistance is very high, which is almost like a open circuit, so no current may flow through the Drain-Source. When Gate-Source potential difference is applied, the Drain-Source resistance is reduced, and there will be current flowing through Drain-Source, which is now a closed circuit.

In a nutshell, a FET is controlled by the Gate-Source voltage applied (which regulates the electrical field across a channel), like pinching or opening a straw and stopping or allowing current flowing. Because of this property, FETs are great for large current flow, and the MOSFET is commonly used as a switch.

Okay, let me summarize the differences between BJT and MOSFET.

• Unlike bipolar transistors, MOSFET is voltage controlled. While BJT is current controlled, the base resistor needs to be carefully calculated according to the amount of current being switched. Not so with a MOSFET. Just apply enough voltage to the gate and the switch operates.
• Because they are voltage controlled, MOSFET have a very high input impedance, so just about anything can drive them.
• MOSFET has high input impedence.

To use a MOSFET as a switch, you have to have its gate voltage (Vgs) higher than the source. If you connect the gate to the source (Vgs=0) it is turned off.

For example we have a IRFZ44N which is a “standard” MOSFET and only turns on when Vgs=10V – 20V. But usually we try not to push it too hard so 10V-15V is common for Vgs for this type of MOSFET.

However if you want to drive this from an Arduino which is running at 5V, you will need a “logic-level” MOSFET that can be turned on at 5V (Vgs = 5V). For example, the ST STP55NF06L. You should also have a resistor in series with the Arduino output to limit the current, since the gate is highly capacitive and can draw a big instantaneous current when you try to turn it on. Around 220 ohms is a good value.

This page shows some detail explanation how a MOSFET works as a switch. This page shows some advanced usage of MOSFET.

MOSFETs come in four different types. There are three main categories we need to know.

• N-Channel (NMOS) or P-Channel (PMOS)
• Enhancement or Depletion mode
• Logic-Level or Normal MOSFET

N-Channel – For an N-Channel MOSFET, the source is connected to ground. To turn the MOSFET on, we need to raise the voltage on the gate. To turn it off we need to connect the gate to ground.

P-Channel – The source is connected to the power rail (Vcc). In order to allow current to flow the Gate needs to be pulled to ground. To turn it off the gate needs to be pulled to Vcc.

Depletion Mode – It requires the Gate-Source voltage ( Vgs ) applied to switch the device “OFF”.

Enhancement Mode – The transistor requires a Gate-Source voltage ( Vgs ) applied to switch the device “ON”.

Despite the variety, the most commonly used type is N-channel enhancement mode.

There are also Logic-Level and Normal MOSFET, but the only difference is the Gate-Source potential level required to drive the MOSFET.

I will try to explain it in the simplest way I can, for more detail or if you are in doubt, check the references and links I provide at the bottom of the post.

MOSFET is a voltage controlled field effect transistor that differs from a JFET. The Gate electrode is electrically insulated from the main semiconductor by a thin layer of insulating material (glass, seriously!). This insulated metal gate is like a plate of a capacitor which has an extremely high input resistance (as high as almost infinite!). Because of the isolation of the Gate there is no current flow into the MOSFET from Gate.

When voltage is applied at the gate, it changes the width of the Drain-Source channel along which charge carriers flow (electron or hole). The wider the channel, the better the device conducts.

The MOSFET are used differently compared to the conventional junction FET.

• The infinite high input impedance makes MOSFETs useful for power amplifiers. The devices are also well suited to high-speed switching applications. Some integrated circuits contain tiny MOSFETs and are used in computers.
• Because the oxide layer is so thin, the MOSFET can be damaged by built up electrostatic charges. In weak-signal radio-frequency work, MOSFET devices do not generally perform as well as other types of FET.

Where to put the load to a MOSFET? Source or Drain?

Because load has resistance, which is basically a resitor. For N-channel MOSFET the reason we usually put the load at the Drain side is because of the Source is usually connected to GND.

If load is connected at the source side, the Vgs will needs to be higher in order to switch the MOSFET, or there will be insufficient current flow between source and drain than expected.

Heat Sink connected to the Drain?

Typically the heat sink on the back of a MOSFET is connected to the Drain! If you mount multiple MOSFETs on a heat sink, they must be electrically isolated from the heat sink! It’s good practice to isolate regardless in case the heat sink is bolted to a grounding frame.

What is the Body Diode For?

MOSFETs also have an internal diode which may allow current to flow unintentionally. The body diode will also limit switching speed. You don’t have to worry about it if you are operating under 1Mhz.

• Theory behind MOSFET (Youtube Video Lecture)

Logic Level P Channel Mosfet

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This tutorial will explore the use of a P-channel and N-channel MOSFETs as a power switch and general transistor theory. This switch will operate on the positive side of a power supply with a negative common. This is for use with 5-volt micro controllers such as Arduino.

Pictured above is the basic electrical connections for Arduino and most modern micro-controllers. We have a negative common and a 5-volt Vcc. That dictates how we connect any driver transistor to the I/O pins. In addition each Arduino I/O pin can source/sink an absolute maximum of 40mA. (Note: operate at 20mA.)

First note that all MOSFETs are voltage operated devices and don't rely on a base current like a bipolar transistor. In many cases gate drive voltages below 5-volts won't work without a bipolar transistor switching in a higher voltage.

Update Dec. 2019. Many micro-controllers today are using 3.3-volt Vcc. This is also true of Raspberry Pi. I found two MOSFETs that work at 3.3-volts.

The IRFZ44N is an N-channel device rated at 55V and RDS(on) resistance of 0.032 Ohms max. The other is a P-channel device rated at 55V and a RDS(on) of 0.02 Ohms max.

See the following spec sheets:

Referring to Plate 1 whenever the voltage difference between the gate (G) and source (S) exceeds around 5-volts this opens a conductive channel between source (S) and drain (D) allowing current flow from the source back to the power supply. (Here we are using electron flow from negative to positive.)

This is often known as a series pass configuration.

Looking again at Plate 1 with no input to the base of Q1 the collector voltage rises to Vcc and with no difference in potential across Rgs Q6 and Q8 are turned off.

Applying 5-volts to the base resistors of Q8 and Q6 (plate 1) forward biases their base-emitter junctions allowing a small current flow Ib. Depending on the DC gain (hfe) of the individual transistors the base current is multiplied to produce Ic. The relationship is as follows:

Ie = Ib + Ic; Ib * hfe = Ic.

The base current Ib is determined by Vin - 0.6 / Rb. The 0.6 volts is the voltage drop across the BE junction. Let's say Q1 and Q7 are 2N2222As that have minimum hfe of 90 and we desire an Ic of 20 mA. Here is how this will work:

Now some issues on switching transistors. We want them operating in their saturation mode where any additional base current will produce no increase in collector current (Ic). When making these calculations a transistor spec sheet gives a range for hfe, assume the lowest value. Next as long as we don't exceed the max base current rating assume extra current. In this case I would use a 2.2K for Rb.

When a bipolar transistor is operating at saturation the emitter-collector voltage equals 0.5V. In the case of MOSFETs Q6 and Q8 we want those operating in saturation mode as well. With a 12-volt difference between gate-source this assures a fast, hard turn on. At saturation MOSFETS such as the IRF630 and IRF9630 have a drain-source resistance of 0.4 and 0.8 ohms respectively.

So Let's find Rgs where we want to drop 11.5 volts:

Let's assume a much higher value of say 10K to assure the desired voltage drop. Again we have lots of room to play with to assure saturation of all four transistors. Note that in reality Rgs sets the current level when Q1 and Q7 are in saturation mode.

MOSFET Gate-Source Breakdown

One final issue is the gate-source breakdown voltage of both MOSFETs or Vgs. For the IRF630 and IRF9630 this is 20 volts. The 24-volts in Fig. A would damage Q8. The 10-volt Zener in series with Q7's collector will keep this within a safe margin.

Uses

There are number of advantages to the above circuits. A low source-drain turn on resistance means more power is delivered to the load and less heating of series pass MOSFETs. The ability to operate at 5-volts makes direct connections to a micro-controller a cinch. In addition this can be pulse-width-modulated to control motor speed on a say H-bridge circuit.

The largest use of these circuits is H-bridge motor controls. They are used in conjunction with N-channel MOSFET switches.

P Channel Power Mosfet

Note that Rg (or Rgs) is used to bleed the charges off the MOSFET gates or else they may not turn off.

Have fun.

I hope the series was helpful. Any corrections, suggestions etc. e-mail me at lewis@bvu.net.

• Related:
• Why Your MOSFET Transistors Get Hot YouTube
• Issues on Connecting MOSFETs in Parallel YouTube
• Simple Circuits for Testing MOSFET Transistors YouTube

Mosfet P Channel Vs N Channel

P Channel Mosfet Depletion

• New Nov. 2014
• Using the ULN2003A Transistor Array with Arduino YouTube
• Using the TIP120 & TIP120 Darlington Transistors with Arduino YouTube
• Using Power MOSFETS with Arduino YouTube
• Using PNP Bipolar Transistors with Arduino, PIC YouTube
• Using NPN Biploar Transistors with Arduino, PIC YouTube
• How to build a Transistor H-Bridge for Arduino, PIC YouTube
• Build a Power MOSFET H-Bridge for Arduino, PIC YouTube