In active-mode, the base-emitter junction is forward-biased.

In active-mode, the base-emitter junction is forward-biased.

• A. False
• B. Not biased
• C. Undetermined
• D. True

Answer: (D)

Active-mode operation requires the base-emitter junction to be forward-biased. When the base-emitter junction is forward-biased (about 0.6–0.7 V for silicon), carriers can be injected from the emitter into the base. In an NPN device, this means the base must sit about a half-volt to seven-tenths of a volt above the emitter; the opposite polarity applies to a PNP device. This forward bias lets a small base current control a much larger collector current (I_C ≈ β I_B) while the base-collector junction remains reverse biased to allow carriers to be swept into the collector. If the base-emitter junction isn’t forward-biased, the transistor won’t conduct in the active region and the device won’t amplify in this mode.

Active-mode operation requires the base-emitter junction to be forward-biased. When the base-emitter junction is forward-biased (about 0.6–0.7 V for silicon), carriers can be injected from the emitter into the base. In an NPN device, this means the base must sit about a half-volt to seven-tenths of a volt above the emitter; the opposite polarity applies to a PNP device. This forward bias lets a small base current control a much larger collector current (I_C ≈ β I_B) while the base-collector junction remains reverse biased to allow carriers to be swept into the collector. If the base-emitter junction isn’t forward-biased, the transistor won’t conduct in the active region and the device won’t amplify in this mode.