Which transistor junction must be reverse-biased to allow collector current to flow in the active region?

Which transistor junction must be reverse-biased to allow collector current to flow in the active region?

• A. Base-Collector forward-biased
• B. Emitter-Base Junction forward-biased
• C. Collector-Base Junction reverse-biased
• D. Emitter-Collector Junction reverse-biased

Answer: (C)

In the active region of a Bipolar Junction Transistor, the base-emitter junction must be forward-biased to inject carriers from the emitter into the base, while the collector-base junction must be reverse-biased to create the electric field that sweeps those carriers into the collector. This reverse bias at the collector-base junction keeps the base–collector barrier high, so most of the carriers injected from the emitter are pulled into the collector, making the collector current controlled by the base current. If the collector-base junction were forward-biased, the transistor would push into saturation, and the collector current would no longer be governed by the base current in the intended way. The emitter-base junction being forward-biased is essential for initiating carrier injection; reversing it stops significant current flow.

In the active region of a Bipolar Junction Transistor, the base-emitter junction must be forward-biased to inject carriers from the emitter into the base, while the collector-base junction must be reverse-biased to create the electric field that sweeps those carriers into the collector. This reverse bias at the collector-base junction keeps the base–collector barrier high, so most of the carriers injected from the emitter are pulled into the collector, making the collector current controlled by the base current.

If the collector-base junction were forward-biased, the transistor would push into saturation, and the collector current would no longer be governed by the base current in the intended way. The emitter-base junction being forward-biased is essential for initiating carrier injection; reversing it stops significant current flow.