How do bipolar junction transistors (BJTs) differ from field-effect transistors (FETs)?

Bipolar junction transistors (BJTs) and field-effect transistors (FETs) are fundamentally different in their operation principles, which is reflected in how they are controlled. BJTs are current-controlled devices, meaning that the output current flowing through the collector-emitter path is regulated by the input current at the base terminal. This current control mechanism allows BJTs to amplify signals effectively in many applications.

On the other hand, FETs are voltage-controlled devices. The operation of an FET is governed by the voltage applied to the gate terminal, which influences the current flowing between the source and drain terminals. This characteristic results in a high input impedance for FETs, making them particularly suited for applications where minimal loading on preceding circuit stages is desired.

The distinction in control mechanisms shapes their applications and performance in various electronic circuits. For instance, BJTs tend to be favored in applications requiring high linearity and gain, particularly in analog circuits, whereas FETs are often used in digital circuits and high-impedance applications due to their voltage control features.

This understanding of BJTs and FETs allows for better circuit design choices based on the specific requirements of the application, making it essential to grasp these fundamental differences.