Analog Electronics
Optocouplers combine

 Power transistor and silicon transistor.
 IGBTs and MOSFETs.
 SITs and BJTs.
  Infrared light emitting diode and a silicon photo transistor.

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Analog Electronics
For transistor action

  all of these.
  the emitter should be heavily doped.
  the base region must be very thin and lightly doped.
  Je must be forward biased and Jc should be reverse biased.

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