Photo transistor is used for:

This question was previously asked in
RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)
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  1. direct coupling
  2. LC coupling
  3. RC coupling
  4. isolation

Answer (Detailed Solution Below)

Option 4 : isolation
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Phototransistor

  • A Phototransistor is an electronic switching and current amplification component which relies on exposure to light to operate.
  • When light falls on the junction, reverse current flows which are proportional to the luminance.
  • Phototransistors are used extensively to detect light pulses and convert them into digital electrical signals.
  • These are operated by light rather than electric current.
  • These devices act like an optoisolator.
  • An optoisolator is an electronic component that transfers electrical signals between two isolated circuits by using light.
  • Opto-isolators prevent high voltages from affecting the system receiving the signal.

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