Bipolar transistors

What is the state of the junctions when a bipolar transistor is in the saturation region?

  1. ABoth the base-emitter and base-collector junctions are forward biased
  2. BBoth junctions are reverse biased
  3. CThe base-emitter junction is reverse biased and the base-collector junction is forward biased
Show answer and explanation

Answer: A. Both the base-emitter and base-collector junctions are forward biased

In saturation, the base-collector junction is forward biased as well as the base-emitter junction. The collector current is limited by the external circuit and hardly increases even if the base current is raised. This is the on state of a switch, with a small VCE of about 0.1 to 0.2 V.

  • A. Correct. Saturation is when both junctions are forward biased.
  • B. Both reverse biased is the cutoff region.
  • C. This combination is reverse-active operation, where the roles of emitter and collector are swapped.
Practice this topic Back to topic

More Bipolar transistors questions

  1. When the output characteristics (IC-VCE) of a common-emitter transistor are plotted with base current IB as a parameter, what is characteristic of the active region?
  2. What does the load line drawn on the output characteristics of a transistor amplifier represent?
  3. Which value is closest to the maximum power efficiency of an ideal class B push-pull amplifier?
  4. In a circuit using a transistor as a switch, what is the main purpose of a resistor in series with the base?
  5. What is the difference between the DC current gain hFE and the small-signal current gain hfe?