Bipolar transistors

What is the role of a coupling capacitor placed between amplifier stages?

  1. ATo amplify the signal
  2. BTo isolate the DC bias of each stage and pass only the AC signal
  3. CTo convert AC to DC
Show answer and explanation

Answer: B. To isolate the DC bias of each stage and pass only the AC signal

A capacitor blocks DC and passes AC. A coupling capacitor between stages keeps the DC bias voltages of the preceding and following stages from affecting each other while passing only the AC signal. Its impedance rises at low frequencies, which also reduces low-frequency gain.

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More Bipolar transistors questions

  1. How does the current gain hFE of a silicon bipolar transistor generally change as temperature rises?
  2. Which condition increases the small-signal input resistance (hie) of a common-emitter amplifier?
  3. What is the advantage of an active load, which uses a transistor acting as a current source instead of a load resistor in an amplifier?
  4. When a switching transistor is turned off from deep saturation, what is the main reason it takes time to turn off?
  5. Which is a typical family of logic ICs built with bipolar transistors?