Transistors: Current vs Voltage Control

The transistor is the building block of active electronics. Bipolar Junction Transistors (BJTs) are current-controlled devices, while Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are voltage-controlled.

In a 2023 power electronics survey, 92% of new power conversion designs utilized MOSFETs or wide-bandgap devices (SiC, GaN) over BJTs due to their superior switching speeds and lower conduction losses.

Key Specifications Data

ParameterBJT (e.g. 2N3904)MOSFET (e.g. 2N7002)
Control MechanismBase CurrentGate Voltage
Input ImpedanceLow to MediumExtremely High
Switching SpeedModerateFast

Frequently Asked Questions

Why use a BJT instead of a MOSFET?

BJTs often provide better linearity in analog audio amplifiers and are more robust against ESD damage during handling.

What is Miller capacitance?

Parasitic capacitance between the gate and drain of a MOSFET that slows down switching times, causing switching losses.

Related Resources