Lecture Notes on MOSFET

Introduction

• Welcome to the Creatrix YouTube Channel
• Target Batch 2.2 Analog Electronics
• Beginning of the new unit on MOSFET
• Discussion on previous topics: Multistage Amplifier, Frequency Response, Differential Amplifier, JFET
• Important for both Analog and Basic Electronics

MOSFET: Introduction

• Full form: Metal Oxide Semiconductor Field Effect Transistor
• Key elements: Metal, Oxide, Semiconductor
• Controlling the device through the electric field
• Comparison between BJT and MOSFET
• Three-terminal device: Gate, Source, Drain

Construction and Structure of MOSFET

• Use of metal, silicon dioxide (SiO2), P and N type semiconductors
• Formation of the channel: controlled by the gate
• Terminals of MOSFET and BJT

Characteristics of MOSFET

• High speed, low size, and power consumption
• Ideal for integrated circuits: used up to VLSI
• Also used as a capacitor

Operating Regions and Modes

1. Cut-off Region: No channel formed
   • V_GS < threshold voltage
   • Current = 0
2. Depletion Mode: Pre-existing channel
   • Controlling the width of the channel by altering gate voltage
   • Direction of current from source to drain
3. Enhancement Mode: Gate terminal forms the channel
   • V_GS > threshold voltage
   • Current flows from drain to source

Characteristics and Equations

• Specific voltage and current characteristics
• Definition of transconductance and output conductance of MOSFET
• Channel length modulation: change in drain current
  • Reason for the formation of the slope

Other Important Points

• Short channel effects and device stability
• Differences between P-channel and N-channel MOSFET
• Small signal model and amplifier applications
• Hybrid pi model

Additional Topics

• Comparison of Early effect: with BJT
• Calculation: Threshold voltages and transconductance factor