Bipolar transistors

Which is a characteristic of a SiGe HBT (heterojunction bipolar transistor)?

  1. AIt is a transistor with a metal base
  2. BThanks to a heterojunction with a SiGe base, it can operate up to high frequencies
  3. CIts current gain is fixed at 1 or less
Show answer and explanation

Answer: B. Thanks to a heterojunction with a SiGe base, it can operate up to high frequencies

A SiGe HBT is a heterojunction bipolar transistor whose base uses SiGe, which has a smaller band gap. The base can be made heavily doped and thin while keeping high emitter injection efficiency, and an electric field can be built into the base to accelerate carriers, so it has excellent high-frequency performance and is used in communication ICs.

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More Bipolar transistors questions

  1. What is the typical collector-emitter voltage of a silicon bipolar transistor in the saturation region?
  2. Which circuit uses two matched transistors to make the current in one transistor equal to the current in the other?
  3. What does a differential pair, with the emitters of two transistors connected to a common current source, do?
  4. What is the approximate transconductance gm of a bipolar transistor operating at a collector current of 1 mA? (Room temperature, thermal voltage VT ≈ 26 mV)
  5. What is the main use of a photocoupler, which combines an LED and a phototransistor in one package?