Introduction to Power Transistor, Types and Its Working

Hello friends I hope you all are doing great. In this post, we will have a detailed look at Introduction to Power Transistor. The transistor is a semiconductor component that first time created in 1947 at Bell Lab. It is the main component of any digital device. The basic function of the transistor is to do amplification of the signal.

It consists of semiconductor substances like silicon or germanium or gallium arsenide. The main two types of transistors are NPN and PNP that are BJT transistors. With the other type of transistor is FET its consists of three terminals. in this post we will cover the pinout working, application and some other related parameters of Power transistor. So let’s get started with Introduction to Power Transistor.

Table of Contents

Introduction to Power Transistor

The symbolic representation of the transistor can be seen in below figure.

The collector to emitter voltage with the collector current characteristic for transistor can be seen here

It can be observed that in the above figure the transistor is a component that’s collector current is directly related to base current at different values of the collector to emitter.
The power transistor are generally used in controls of different machines to off and on the supply.

The transistor consists of a resistive load can see here.

The Ic-Vce curve can be seen here having a load line of resistance load.

The base current IB4 will totally get on the transistor and the base current of 0 will totally off the transistor.
If the value of base current of the transistor has a similar value to the IB3 then the transistor will not completely off no run.
It no wanted to state because the larger collector current passes from the larger collector to emitter causing the very high-value power of the transistor.
To make sure the transistor operates without losing power it is compulsory to has base current larger value than totally do saturation of the transistor.

Power transistor are generally employed in inverters circuitry The main disadvantage in switching applications is that high power transistor has less operating speed in varying on to off state as the comparatively high base current will give or eliminated when it gets on and off.

Insulated-Gate Bipolar Transistor

The IGBT is created in some years ago or can say new to electronic industries. It is like to the power transistor with the difference that it can regulate through voltage given at gate than the current passing in the base that happens in the power transistor.
The impudence of the control gate has a larger value at IGBT.
Therefore the quantity of current passing in the gate is very less. The component is equivalent to the collaboration MOSFET and power transistor.
The symbol of IGBT can be seen here.

As the IGBT is regulated from the gate voltage having less current movement so its switching can be done with high speed over the normal power transistor.
IGBT is so employed in such applications where high power frequency is needed.

Power and Speed Comparison of Power Electronic Components

The below figure indicates the comparison between relative speeds and power handling features of SCR, power transistor, and GTO thyristors.
We can see that the SCR has the ability of large power function over other components. GTO thyristor can work at large power and with high speed than SCRs.
So power transistors can bear less power as compared to the other category of thyristor but its switching speed is larger ten-time high.

Types of Power Transistors

Bipolar Junction Transistors (BJTs)

This type of transistor comes with the capacity for handling two polarities. BJT transistors are used as amplifiers and switching circuits.
It is normally used for current control and also controls switching on and off states and ramifications. BJT was first made in 1948 by William Shockley.
The BJT emitter has a high doping level and the base is moderately doped while the collector is lightly doped.
There are two junctions; it has an emitter base and a collector base.
The main types of BJT transistors are NPN and PNP transistors.
- BJT comes larger and has a high current for flow.
- It also has a high breakdown voltage. It handles high current-carrying features.
- It is used for high-power circuits.

Metal Oxide Semiconductor Field-Effect Transistor

MOSFET is a type of FET transistor, and it comes with three pins as BJT has. MOSFET pins are source, base, and drain.
MOSFET working is based on channel width.
High-width channel of MOSFET has high efficiency.
• The metal oxide semiconductor field effect transistor is used as a voltage controller and does not use any input current.
It also has high input impedance.

Static Induction Transistor (SITs)

it is vertically configured that comes with 3 pins. As compared to FET static induction transistors come with high voltage breakdown.
This transistor has high power and high frequency with a small multichannel.
It is used for getting high breakdown voltage as compared to FET. It has a short channel length with low noise.
It also has low terminal resistance.

Insulated Gate Bipolar Transistor (IGBTs)

IGBT comes with semiconductor materials and three pins. It is normally used for switching circuits. The insulated bipolar transistor comes with four layers of PNPN that are regulated with a metallic oxide semiconductor (MOS) gate structure. It provide high current gain

Power Transistor Features

It has 3 pins and part of advanced circuits.
It has low fault voltage and high speed for switching.
Its working is based on full voltage.
It works well for high current and power. It is larger size transistor.
Its IC value is 3 amperes, and collector to emitter is 50 volts.
Its collector-to-base voltage is 50Volts with emitter to base is4Volts.

Advantages

The power transistor working frequency is about 10 to 15 kHz.
It has high voltage gain and high current density.
Forward voltage for this transistor is low and carries larger current for on state and block high voltage for off state.
It can easily be turned on and off with larger bandwidth gain for this transistor.
It has low voltage for on-state and regulated power that provided to connected load.

Disadvantages

It has high noise and also low thermal stability.
The reverse blocking features of this transistor are also low.
It can be broken due to the 2nd breakdown.
It needed complicated circuits and has low-efficiency
It is high weight and high cost.
Its switching speed is low.
It has high voltage and current ratings

Applications

It is part of amplifier circuits also used for audio frequency amplifiers circuits with RF circuits.
It is used for slew rate devices, push-pull circuits and for proving high current.
It is part of the intermediate Power switch and medium power switch.
It is used for relays, SMPS, power amplifiers, converters and power control circuits.
It is used in power regulators and controllers.
It is used for microprocessors

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