Explain the operation of a bipolar junction tra... - SS2 Physics Electronics Question

A bipolar junction transistor (BJT) is a three-terminal device consisting of two pn junctions. It operates based on the principle of minority carrier injection. The BJT has three modes of operation: cutoff, active, and saturation. In the cutoff mode, both the base-emitter and base-collector junctions are reverse-biassed, and no current flows through the transistor. In the active mode, the base-emitter junction is forward biassed, allowing current to flow from the emitter to the base. The transistor acts as an amplifier in this mode. In the saturation mode, both junctions are forward biassed, and the transistor acts as a switch.

 

BJTs have various applications, including amplification, switching, and oscillation. In amplification, the BJT is used to amplify weak signals, such as audio or radio signals, to a higher power level. In switching applications, the BJT acts as an electronic switch to control the flow of current through a circuit. BJT-based oscillators generate continuous waveforms used in applications like radio frequency (RF) communication. BJT amplifiers and switches find widespread use in electronic devices, such as audio amplifiers, televisions, computers, and mobile phones.