Bipolar transistors

When a switching transistor is turned off from deep saturation, what is the main reason it takes time to turn off?

  1. AThe transistor's temperature drops
  2. BThe junction capacitance becomes zero
  3. CIt takes time to remove the excess minority carriers stored in the base region
Show answer and explanation

Answer: C. It takes time to remove the excess minority carriers stored in the base region

In saturation, more minority carriers than necessary are stored in the base region. Even when the transistor is driven off, the collector current keeps flowing until these carriers are removed (the storage time). Clamping with a Schottky diode to prevent deep saturation is one way to speed it up.

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More Bipolar transistors questions

  1. Which is a typical family of logic ICs built with bipolar transistors?
  2. Which pairing of a technology that integrates bipolar transistors and CMOS on the same chip with its purpose is correct?
  3. Which set correctly names the three terminals of a bipolar transistor?
  4. In the circuit symbol of an NPN transistor, which way does the arrow on the emitter point?
  5. Which correctly relates the emitter current IE, base current IB and collector current IC of a bipolar transistor?