Bipolar transistors

Which correctly describes the Early effect in a bipolar transistor?

  1. AThe current gain falls as temperature rises
  2. BAs the collector-base reverse bias increases, the effective base width narrows and the collector current increases
  3. CBase current flows when light shines on the device
Show answer and explanation

Answer: B. As the collector-base reverse bias increases, the effective base width narrows and the collector current increases

Increasing the collector voltage spreads the depletion layer of the collector-base junction into the base, narrowing the effective base width. As a result, recombination in the base decreases and the collector current increases slightly for the same base current. This is the Early effect, which makes the output characteristics slope instead of being flat.

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More Bipolar transistors questions

  1. Which is a characteristic of a Darlington connection of two transistors?
  2. In a PNP transistor, which carriers are injected from the emitter into the base and mainly carry the current?
  3. Which is a characteristic of a common-collector amplifier (emitter follower)?
  4. Which is a characteristic of a common-base amplifier?
  5. What does the transition frequency fT of a bipolar transistor mean?