The Basic lessons · Circuit components · B-004-003

The Bipolar Transistor: Amplifier and Switch

Learn how the bipolar transistor uses a small electrical signal to control a larger one, acting as both an amplifier and a switch. Understand the roles of its three parts, the difference between NPN and PNP types, and why heat is its biggest enemy.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-004-003.

What this subsection asks

• Which of these components can amplify a small signal using low voltages?
• What term describes the most basic semiconductor component used to amplify?
• What are the three electrodes of a bipolar transistor?
• If a low-level signal is placed at the input to a transistor and a higher level of the signal is produced at the output, what is this effect called?
• What prevents the substitution of a PNP transistor with an NPN transistor?
• A semiconductor device is labelled as a "general purpose audio NPN device." What is it?
• What are the two basic types of bipolar transistors?
• Which of these operating conditions is most likely to cause a transistor to fail?
• Which electrode of the bipolar transistor controls the output current?
• When a bipolar transistor is used as a switch, which electrode controls its state?
• If a transistor is alternatively driven into saturation and cut-off, what does it behave like?