MOSFET in Physics: Definition, Working, Types & Applications

The topic of MOSFET is important in physics and helps us understand how modern electronic devices amplify signals, switch circuits, and process information in computers and gadgets. MOSFETs are used everywhere, from simple toys to advanced communication and power electronics.

Understanding MOSFET

MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. It is a type of field-effect transistor (FET) used to control the flow of current in circuits. MOSFETs have three main terminals: gate, drain, and source. They are different from typical bipolar junction transistors (BJTs) because MOSFETs are controlled by voltage at the gate terminal, not by current. This makes them energy-efficient and perfect for high-speed switching in devices like microprocessors, mobile phones, and amplifiers. MOSFETs are also used in physics experiments and are crucial for understanding modern semiconductor technology, semiconductor circuits, and transistor types.

Formula or Working Principle of MOSFET

MOSFET operation is based on the principle of an electric field, which controls the width of a channel where current flows. The main working formula for MOSFETs (especially in the linear or ohmic region) is:

Drain Current (I_D) = μC_ox(W/L)[(V_GS-V_TH)V_DS - (V_DS²/2)]

Here’s how it works in a physical system: When a voltage is applied between gate and source (V_GS), it creates an electric field that opens or closes the current path between source and drain, acting as a switch or amplifier.

Here’s a useful table to understand MOSFET better:

MOSFET Table

Worked Example / Practical Experiment

Let’s solve a problem or understand an experiment step by step:

1. Identify the known values: For a MOSFET, suppose V_GS = 5V, V_DS = 10V, and V_TH (threshold voltage) = 2V.

2. Apply the correct formula: Use the MOSFET linear region current formula above.

3. Substitute the values and calculate drain current (I_D).

4. Analyze the physical meaning: If V_GS exceeds V_TH, the MOSFET turns ON and allows current.

Conclusion: This approach helps apply MOSFET equations and concepts in real exam problems and physics circuits.

Practice Questions

• Define MOSFET with an example circuit.
• What formula is used in MOSFET theory?
• How does a MOSFET affect power supplies or amplifiers?
• Write the working principle behind MOSFET operation.
• List the differences between MOSFET and BJT.

Common Mistakes to Avoid

• Misinterpreting the MOSFET symbol or gate/drain/source pinout in exam diagrams.
• Confusing voltage control (MOSFET) with current control (BJT).
• Applying the wrong region formula (linear/saturation) for MOSFET in calculations.
• Forgetting the direction of current in N-channel vs P-channel MOSFETs.

Real-World Applications

MOSFET is widely used in electronics, power supply circuits, switching regulators, and audio systems. They are also used in robotics, automobile electronics, and communication systems. At Vedantu, you can learn how MOSFETs integrate into larger technological solutions and how their use makes devices more efficient and reliable. For more on related circuit uses, check rectifier applications and Ohm's Law in circuits.

In this article, we explored MOSFET — its meaning, formula, practical relevance, comparison with BJT, and usage in physics. Keep exploring such topics with Vedantu to improve your understanding of modern electronics and physics syllabi.

Related topics to broaden your knowledge: Semiconductor Diode, BJT, NPN vs PNP Transistor, and Varactor Diode.