🔍 Key Concepts

• Class A amplifier biasing for bipolar junction transistors (BJTs) • Conduction path in an NPN transistor (emitter–base–collector) under normal active operation • Meaning of forward biased vs reverse biased PN junctions in a BJT used as a linear amplifier

💭 Think About

• In normal active (linear) operation of an NPN transistor, which junction must allow current to flow easily so that small base current changes control a larger collector current? • For a transistor to stay in its linear (Class A) region and not in cutoff or saturation, how is the collector-base junction typically biased? • If both transistor junctions were forward biased, would that look more like saturation, cutoff, or linear amplification?

✅ Before You Answer

• Confirm how an NPN transistor is oriented: emitter (N), base (P), collector (N), and which side of each junction is connected to the more positive potential in active operation. • Verify which junction condition (forward bias) corresponds to a low resistance, current-controlling input, and which (reverse bias) corresponds to a high resistance, output region for voltage amplification. • Eliminate any option where the bias conditions would force the transistor into saturation (both junctions forward biased) or cutoff (both junctions reverse biased), rather than active (Class A) operation.