What is the difference between BJT and MOSFET, and why do we mostly use MOSFET?

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BJT: Bipolar Junction Transistor MOSFET: Metal Oxide Semiconductor Field-Effect Transistor. A BJT has an emitter, collector, and base, while a MOSFET has a gate, source, and drain. BJTs are preferred for low current applications, while MOSFETs are for high power functions. In digital and analog circuits, MOSFETs are commonly used. The operation of MOSFET depends on the voltage at the oxide-insulated gate electrode, while the operation of BJT is dependent on the current at the base.

In BJT, the operation is controlled by the base current. Providing constant voltage in electrical circuits is easier than providing constant current. So MOSFETs' gate drive circuit is less complex than BJT’s base drive circuit.

In high-frequency applications, the switching loss is a major impact on the total power loss of the circuit, the MOSFETs are preferred. However, for applications having lower operating frequencies, BJT is preferred..

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