Power Transistors MOSFETs and IGBTs
Power Transistor
A current-controlled power switching device used in medium-power applications.
Working Principle
A power transistor controls a large collector current with a small base current. When a base current is applied, the transistor turns ON and allows current to flow from collector to emitter. Removing the base drive turns it OFF. Because it is current-controlled, the drive circuit must supply enough base current for reliable switching.
Main Features
>Three terminals: base, collector, emitter.
>Current-controlled device.
>Used in amplification and switching.
>Suitable for moderate power levels.
Applications
Power transistors are used in motor control, power amplifiers, DC-DC/AC converters, and low-to-medium power switching circuits. They are less common in modern high-power systems because MOSFETs and IGBTs offer easier gate drive and better switching performance.
MOSFET
A voltage-controlled power device known for fast switching and high input impedance.
Working Principle
A MOSFET is controlled by gate voltage, not gate current. When gate-to-source voltage exceeds the threshold, a conducting channel forms between drain and source. This allows current flow with very little input power. It is a majority-carrier device, so switching is very fast.
Main Features
>Three terminals: gate, drain, source.
>Voltage-controlled device.
>Very high input impedance.
>Excellent for high-frequency switching.
Applications
MOSFETs are widely used in switch-mode power supplies, DC motor drives, battery-powered equipment, and low- to medium-voltage converters. Their fast switching and low drive requirement make them ideal for efficient modern power electronics.
IGBT
A hybrid power device that combines MOSFET gate control with bipolar conduction.
Working Principle
An IGBT uses a voltage-controlled gate like a MOSFET, but its output conduction resembles a bipolar transistor. When a positive gate voltage is applied, a channel is formed, and the device turns ON. It offers low conduction loss at high voltage and high current, which makes it very useful in power conversion.
Main Features
>Three terminals: gate, collector, emitter.
>Voltage-controlled gate with high input impedance.
>Good for high voltage and high current.
>Preferred in motor drives and inverters.
Applications
IGBTs are used in industrial drives, EV inverters, UPS systems, traction systems, and induction heating. They are chosen when the circuit needs high power handling with simpler gate drive than a power transistor and better high-voltage performance than a MOSFET.
