Bipolar transistors

Which is a characteristic of a common-collector amplifier (emitter follower)?

  1. AIts voltage gain is very large
  2. BIts output phase is inverted from the input
  3. CIts voltage gain is about 1 and its output impedance is low, so it is used as a buffer
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Answer: C. Its voltage gain is about 1 and its output impedance is low, so it is used as a buffer

In an emitter follower, the emitter voltage follows the base voltage at a level lower by VBE, so the voltage gain is about 1 and the phase is the same. With high input impedance and low output impedance, it is used as a buffer for impedance conversion.

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More Bipolar transistors questions

  1. Which is a characteristic of a common-base amplifier?
  2. What does the transition frequency fT of a bipolar transistor mean?
  3. Which correctly describes thermal runaway in a bipolar transistor?
  4. Which is a characteristic of a SiGe HBT (heterojunction bipolar transistor)?
  5. What is the typical collector-emitter voltage of a silicon bipolar transistor in the saturation region?