🔍 Key Concepts

• Bipolar junction transistor (BJT) terminals: emitter, base, collector • Relationship between input current and output current in a transistor • Definition of current gain (β) in a BJT

💭 Think About

• Which transistor terminal current is treated as the input that controls the device, and which terminal current is considered the output? • In a common-emitter configuration, which ratio of currents is used to describe how much the transistor amplifies current? • Look at each option and ask: does this represent an input-to-output current gain, or something else?

✅ Before You Answer

• Identify which current (base, collector, or emitter) is the control/input current in a BJT. • Identify which current (base, collector, or emitter) is the output current you care about in most amplifier circuits. • Make sure the ratio is written as output current divided by input current, not the other way around.