Bipolar transistors

What is the state of the junctions when a bipolar transistor is in the cutoff region (off)?

  1. AThe base-emitter junction is forward biased and the base-collector junction is reverse biased
  2. BBoth junctions are forward biased
  3. CBoth the base-emitter and base-collector junctions are reverse biased
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Answer: C. Both the base-emitter and base-collector junctions are reverse biased

In the cutoff region, both the base-emitter and base-collector junctions are reverse biased (or the base-emitter voltage does not reach the forward voltage), and almost no collector current flows. This is the off state when the transistor is used as a switch.

  • A. This combination is the active region, used for amplification.
  • B. Both junctions forward biased is the saturation region.
  • C. Correct. Cutoff is when both junctions are reverse biased.
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More Bipolar transistors questions

  1. What is the typical base-emitter voltage VBE of a silicon bipolar transistor operating in the active region?
  2. What is the collector dissipation of a transistor operating at a collector-emitter voltage of 5 V and a collector current of 100 mA?
  3. Which correctly describes the difference in how bipolar transistors and MOSFETs are controlled?
  4. In a common-emitter amplifier with transconductance gm = 40 mS and collector resistor RC = 5 kΩ, roughly what is the magnitude of the voltage gain? (Ignore the load.)
  5. What is the state of the junctions when a bipolar transistor is in the saturation region?