Transistors

The power transistors have controlled turn-on and turn off characteristics. The switching speed of power transistor as much nigher than that of thyristors, and they are extensively used in dc-dc and dc-ac converters. The power transistors can classified as BJT, MOSFETs, SITs and IGBTs

• Transistors are able to amplify the power of a signal
• Bipolar Junction Transistors in which include NPN and PNP transistors are further classified based on their applications and characteristics:
• NPN Transistor: The NPN transistor is commonly used for the amplification and switching in electronic circuits. It is named after the arrangement of its layers: N-type collector, P-type base, and N-type emitter.
• PNP Transistor: The PNP transistor is also used for the amplification and switching but with the opposite current flow compared to NPN.

The terminals of the BJT bipolar transistor are:

• B: Base
• C: Collector
• E: Emitter

Applications of Transistors

• They are used in amplifiers.
• They are used in digital logic circuits.
• They are used in voltage regulators.
• They are used in Logic Circuits
• They are used in Temperature Control Systems
• It is used in converters.
• They are used in automatic switches

MOSFET (Metal–Oxide–Semiconductor Field-Effect Transistor)

The MOSFET is a field-effect transistor and it is a four terminal device with source(S), gate (G), drain (D) and body (B) terminals. It’s generally classified into two basic configurations: Depletion Mode MOSFET and Enhancement Mode MOSFET.

The logic gates are the basic building blocks of all digital circuits and computers. These logic gates are implemented using transistors called MOSFETs. A MOSFET transistor is a voltage-controlled switch. The MOSFET acts as a switch and turns on or off depending on whether the voltage on it is either high or low. There are two types of MOSFETs: NMOS and PMOS. The NMOS turns on when the voltage is high and off when the voltage is low.

Working of MOSFET Transistor

A MOSFET’s operation is dependent on its MOS capacitor. The heart of the MOS-FET is the MOS capacitor. Between the source and drain terminals is where the semiconductor surface is situated at the bottom of the oxide layer. Positive or negative gate voltages can be applied to convert it from p-type to n-type.

Positive gate voltage exerts a repulsive force on the holes beneath the oxide layer, pushing the holes downward along with the substrate.

This depletion region is filled with bound negative charges connected to the acceptor atoms. Once the electrons arrive, a channel is created. Electrons from the drain and n+ source regions are also drawn into the channel by the positive voltage.

The current now flows freely between the source and drain and the gate voltage regulates the electrons in the channel if a voltage is applied between the drain and source. A hole channel under the oxide layer will form if we apply a negative voltage.

Bipolar Junction Transistors (BJT)

A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device used for signal amplification and switching. Based on the arrangement of the semiconductor layers and the direction of current flow, BJTs are classified as NPN (Negative-Positive-Negative) or PNP (Positive-Negative-Positive).

Bipolar Junction Transistors in which include NPN and PNP transistors are further classified based on their applications and characteristics:

• NPN Transistor: The NPN transistor is commonly used for the amplification and switching in electronic circuits. It is named after the arrangement of its layers: N-type collector, P-type base, and N-type emitter.
• PNP Transistor: The PNP transistor is also used for the amplification and switching but with the opposite current flow compared to NPN.

Working of BJT Transistor

• The operation of a PNP transistor is based on the control of current flow between the emitter and collector by the current flowing into the base. Here’s a brief overview:
• When a positive voltage is applied to base-emitter junction. it allows the flow of electrons from emitter to the base.
• The flow of electrons from the emitter to the base creates a path for majority charge carriers to flow from collector to the emitter.
• This controlled flow of holes from the collector to emitter constitutes the output current and it can be amplified based on current flowing into the base.

Insulated Gate Bipolar Transistor(IGBT)

IGBT stands for Insulated Gate Bipolar Transistor. It is a type of power transistor that integrates an input MOS (Metal-Oxide-Semiconductor) with an output bipolar transistor. It is commonly employed as a switching device in inverter circuits, facilitating the conversion of DC (Direct Current) to AC (Alternating Current) power.

• The IGBT combines the input characteristics of a MOSFET with the output characteristics of a BJT, resembling the structure of an N-channel MOSFET and a PNP BJT in Darlington configuration. Additionally, the resistance of the drift region can be integrated.

Working of IGBT

IGBT has three terminals collector (C), emitter (E) and gate (G). These terminals serve distinct roles in controlling current flow through the device. IGBT Operation. In the operation of an IGBT, the collector-emitter connection is established with the collector at a positive voltage compared to the emitter. These forward biases junction J1 and reverse biases junction J2. Notably, there is no voltage applied to the gate at this stage. Due to the reverse bias at J2, the IGBT remains in the off state, preventing any current flow between the collector and emitter. When a positive gate voltage (VG) is applied relative to the emitter, negative charges accumulate beneath the SiO2­ layer due to capacitance. As VG increases, more charges accumulate, forming a layer in the upper P-region when VG exceeds the threshold voltage.

In electronic components, Power Semiconductor Devices are electronic devices that need an external power source to operate actively. Materials used to make semiconductor devices are neither excellent insulators nor conductors. They mainly manipulate, amplify, switch, or control the flow of electric current or voltage in a circuit. Power Semiconductor Devices, like diodes, transistors, thyristors, and sensors require power to do their job. A circuit is an interconnection of components. These components are capable of performing active functions like amplification, rectification, and switching they are called Power Semiconductor Devices.

In this article, we will be going through Semiconductor Devices Which are mainly divided into Diodes, Thyristors and Transistors. Semiconductor Devices are Classified into Two-Terminals, Three-Terminals and Four-Terminals Devices, We will go in-depth about these Devices. We will go through working of diodes, Thyristors, Transistors and Look at Its vi characteristics, At last we will conclude our Article with Advantages, Disadvantages, Applications, and Some FAQs.