Azerbaijan State Oil and
Industry
University
Names: Ömər Zülfüqarlı
Cavid Zamanlı
İskəndərbəyli Fatimə
Group number: 510.23E
Topic: Metal-oxide Semiconductor
Field-effect
Transistors(MOSFET)Transistors
What is a MOSFET ?
A MOSFET, or Metal-Oxide Semiconductor Field-Effect
Transistor, is one of the most widely used types of
transistors in modern electronics. It's a tiny electronic
switch that controls the flow of current using voltage,
rather than current like traditional bipolar junction
transistors.
Thanks to its high efficiency and scalability, the
MOSFET has become the building block of countless
digital circuits, from microprocessors and memory chips
to power supplies and mobile devices. Its ability to
switch rapidly and consume very little power makes it
essential in both high-speed and low-power applications.
History & Development
The MOSFET was invented in 1959 by two
scientists named Mohamed Atalla and Dawon
Kahng. They worked at a place called Bell Labs,
where many important electronics were created.
The MOSFET was special because it was small,
easy to make, and used very little energy. This
made it perfect for building tiny, powerful
machines like computers, phones, and
calculators. Over time, it became one of the most
important parts in electronics we use every day.
MOSFET Structure
A MOSFET has four main parts: Gate, Source, Drain,
and Substrate. The Gate is like a control switch. It
decides if electricity can flow or not. The Source is
where the electricity comes from, and the Drain is
where it goes. The Substrate is the base that holds
everything together.
There is also a very thin layer of material (called
oxide) between the Gate and the Substrate. This
layer keeps electricity from flowing directly through
the Gate, which helps the MOSFET use very little
power.
Types of MOSFETs
There are two main kinds of MOSFETs:
1. N-Channel MOSFET – This type lets electricity flow
when a positive voltage is given to the gate. It works faster
and is used more often.
2. P-Channel MOSFET – This type allows electricity to
flow when a negative voltage is given to the gate.
Each of these has two types of modes:
• Enhancement Mode – The MOSFET is OFF until you turn
it ON with the gate voltage.
• Depletion Mode – The MOSFET is ON by default and can
be turned OFF with the gate voltage.
These types give engineers more options depending on what
a circuit needs.
Working Principle
A MOSFET works like a switch that controls
electricity. You turn it ON or OFF by adding
voltage to the Gate.
When you put the right voltage on the Gate, it creates a
path for electricity to flow from the Source to the
Drain. If there is no voltage, the path stays closed,
and no current flows.
The best part is that the Gate doesn’t need much
energy to work because the thin oxide layer stops
electricity from going into the Gate. This makes the
MOSFET very good at saving power.
Operating Regions
A MOSFET can work in three different ways, called
operating regions:
1. Cut-off Region – The MOSFET is OFF. No electricity
flows because the Gate doesn't have enough voltage.
2. Linear (or Triode) Region – The MOSFET is partly
ON. It acts like a resistor, and electricity flows with some
control.
3. Saturation Region – The MOSFET is fully ON. It allows
a steady flow of electricity from the Source to the Drain.
Each region is useful for different jobs, like turning things
on and off or controlling how much current flows.
Characteristics of MOSFETs
•High Input Impedance: Draws minimal input current, ideal for
low-power use.
•Voltage-Controlled: Operated by voltage, not current—more
efficient than BJTs.
•Fast Switching: Suitable for high-speed, high-frequency circuits.
•Low On-Resistance: Reduces power loss when conducting.
•Types: N-channel and P-channel used in varied applications
(e.g., CMOS).
•Thermal Stability: Performs reliably at high temperatures.
•Compact Size: Enables smaller, more efficient ICs and
processors.
Applications of MOSFETs
• MOSFET as a Switch: MOSFETs can be used as switches to control the flow of
current. When the gate voltage is zero, the channel is not formed, and no current flows
between the source and drain. When a positive voltage is applied to the gate of an N-
channel MOSFET or a negative voltage is applied to the gate of a P-channel MOSFET,
the channel is formed, and current flows between the source and drain.
• MOSFET as an Amplifier: MOSFETs can also be used as amplifiers to increase the
strength of a signal. When a small voltage is applied to the gate, it can produce a large
change in current between the source and drain. This property makes MOSFETs very
useful in electronic circuits.
• It is used as an inverter.
• It is used in digital circuits.
• It is used as a passive element, like in an inductor, resistor, and capacitor.
• It is used as a high-frequency amplifier.
• It is used in brushless DC motor drives.
• It is used in electronic DC relays.
• It is used in SMPS.
• It is used as a switch and in amplifying electronic signals in an electronic device.
Advantages and Disadvantages
Advantages of MOSFETs:
• High Efficiency: Low power consumption and minimal on-resistance.
• Fast Switching: Ideal for high-speed applications.
• High Input Impedance: Perfect for low-power and sensitive circuits.
• Scalable: Can be miniaturized for compact designs.
• Thermal Stability: Operates well in high-temperature environments.
Disadvantages of MOSFETs:
• Sensitive to ESD: Can be damaged by static discharge.
• Limited Current Handling: Not ideal for very high currents.
• Complex Manufacturing: Precision required, increasing cost.
• Gate Leakage: Potential issue in ultra-small designs.
References
1. Electronics Tutorials. (n.d.). MOSFET Basics, Characteristics &
Working. Retrieved from:
https://www.electronics-tutorials.ws/transistor/tran_7.html
2. GeeksforGeeks. (n.d.). MOSFET Characteristics. Retrieved from:
https://www.geeksforgeeks.org/mosfet-characteristics/
3. Element14 Community. (n.d.). Reading MOSFET Curves. Retrieved
from:
https://community.element14.com/challenges-projects/element14-
presents/workbenchwednesdays/b/blog/posts/reading-mosfet-curves
THANK YOU FOR YOUR ATTENTION.
