Darlington pair

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This is two transistors connected together so that the amplified current from the first is amplified further by the second transistor. This gives the darlington pair a very high current gain such as 10000. Darlington pair are sold as complete packages containing the two transistors. They have three leads (BC and E) which are equivalent to the leads of a standard individual transistor.

Darlington pair

You can make up your own darlington pair from two transistors.

For example:

  • For TR1 use BC548B with hFE1 = 220.
  • For TR2 use BC639 with hFE2 = 40.

The overall gain of this pair is hFE1 × hFE2 = 220 × 40 = 8800.

The pair's maximum collector current IC(max) is the same as TR2.

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