Bipolar transistors

Which is a characteristic of a common-base amplifier?

  1. AIts current gain is about 1, but it amplifies well up to high frequencies
  2. BIt has the highest current gain of the three configurations
  3. CIt has the highest input impedance of the three configurations
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Answer: A. Its current gain is about 1, but it amplifies well up to high frequencies

In the common-base configuration, the input emitter current and the output collector current are nearly equal, so the current gain is α (about 1). Its input impedance is low, but it is less affected by feedback capacitance between output and input, so it amplifies well up to high frequencies and is used in RF circuits.

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More Bipolar transistors questions

  1. What does the transition frequency fT of a bipolar transistor mean?
  2. Which correctly describes thermal runaway in a bipolar transistor?
  3. Which is a characteristic of a SiGe HBT (heterojunction bipolar transistor)?
  4. What is the typical collector-emitter voltage of a silicon bipolar transistor in the saturation region?
  5. Which circuit uses two matched transistors to make the current in one transistor equal to the current in the other?