A field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current. There are several types of FETs that are used for different applications, such as MOSFETs which can be found in power electronics and digital circuits, JFETs which are used for signal amplification, and MESFETs which are used for microwave amplification. FETs have advantages over bipolar junction transistors like high input impedance and low noise, but are more sensitive to temperature changes. Research is ongoing to improve FET performance and explore new applications in areas like quantum computing and terahertz electronics.

1. Field Effect Transistor
A field-effect transistor, or FET, is a type of transistor used for amplifying or
switching electronic signals. In this presentation, we will explore the different
types of FETs, their working principles, and their applications.
by Satyasis Mishra

2. MOSFET
Power MOSFETs
Used in power electronics, from electric vehicles to
power supplies.
CMOS transistors
Used in digital circuits, from processors to memory
chips.
Metal-Oxide-Semiconductor Field-Effect Transistors, or MOSFETs, come in many varieties for different
applications. They can be found in power electronics, such as electric vehicles and power supplies, as well as
in digital circuits, such as processors and memory chips.

3. JFET
Amplification
Used for signal amplification in audio and radio frequency (RF) circuits.
Sensitivity
Sensitive to voltage so can be used for touch switches and digital potentiometers.
Low-Noise performance
Used in low-noise high-impedance preamplifiers applications.
Junction Field-Effect Transistors, or JFETs, are used for signal amplification in audio and radio
frequency circuits because of their high input impedance. Due to their sensitivity to voltage, they are
also used for touch switches and digital potentiometers. Low-noise, high-impedance preamplifiers is
another application of JFETs.

4. MESFET
1 Analog Amplifiers
Used for microwave and millimeter-wave amplification.
2 Integrated Circuits
Used in integrated circuits, such as those made from gallium arsenide.
3 RF Switches
Used in microwave/millimeter-wave switches, such as those used in wireless devices.
Metal Semiconductor Field-Effect Transistors, or MESFETs, are used for microwave and millimeter-wave
amplification. They are also used in integrated circuits, such as those made from gallium arsenide, and in
microwave/millimeter-wave switches for wireless devices.

5. Principle
N-Channel FET
On applying a positive voltage to the gate, an
electric field is produced that reduces the resistance
of the channel.
P-Channel FET
On applying a negative voltage to the gate, an
electric field is produced that increases the
resistance of the channel.
The principle of the FET is based on controlling the flow of current through a semiconductor channel using an
electric field. When a voltage is applied to the gate, an electric field is produced that either reduces or
increases the resistance of the semiconductor channel, depending on the type of FET.

6. Applications
1 Amplifiers
FETs are used for signal
amplification in audio and
radio frequency circuits.
2 Switches
FETs are used as
switches in power
electronics and in
microwave/millimeter-
wave switches for
wireless devices.
3 Sensors
Due to their sensitivity to
voltage, FETs are used
as sensors for touch
switches and digital
potentiometers.
Field-effect transistors (FETs) have a wide range of applications, including signal amplification, power
electronics, microwave/millimeter-wave switches, and as sensors for touch switches and digital
potentiometers.

7. Advantages & Disadvantages
Advantages
• High input impedance - low loading effect
• High-frequency response
• Low noise
• No biasing needed
Disadvantages
• Sensitivity to temperature changes
• Less rugged than BJTs
• No beta - more susceptible to
variations in manufacturing
Field-Effect Transistors (FETs) have several advantages over bipolar junction transistors (BJTs), including
high input impedance, high-frequency response, low noise, and no biasing needed. However, FETs are
sensitive to temperature changes, less rugged than BJTs, and more susceptible to variations in
manufacturing.

8. Comparison with BJTs
Property Bipolar Junction Transistor
(BJT)
Field-Effect Transistor (FET)
Principle of operation Current controlled Voltage controlled
Input impedance Low High
Gain (beta) High No beta
Noise High Low
Switching speed Low to moderate High
FETs and Bipolar Junction Transistors (BJTs) have different principles of operation, with BJTs being current
controlled and FETs being voltage controlled. FETs have a higher input impedance, lower noise, and faster
switching speed than BJTs. However, BJTs have a high gain (beta) while FETs do not.

9. Future Prospects
1 Improving FET Performance
Research is focused on reducing power consumption, improving noise performance,
increasing the frequency range, and extending the lifetime of FETs.
2 New Applications
FETs are being explored for applications in quantum computing, terahertz-frequency
electronics, and energy efficiency in power electronics.
3 New FET Technologies
New materials, such as 2D materials and organic semiconductors, are being explored for
use in FETs.
The future of FET technology is bright, with research focused on improving performance, exploring new
applications, and developing new FET technologies using materials such as 2D materials and organic
semiconductors. FETs are being explored for use in quantum computing, terahertz-frequency electronics,
and for improving energy efficiency in power electronics.