Which among the following devices is a P-N junction diode with 3 terminals, as per construction

This question was previously asked in
RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)
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  1. BJT
  2. FET
  3. UJT
  4. SCR

Answer (Detailed Solution Below)

Option 3 : UJT
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Detailed Solution

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The answer is 3) UJT 

A Unijunction Transistor (UJT) is a three-terminal semiconductor device that consists of a single P-N junction formed between a thin P-type base region and an N-type emitter region. The other terminal is connected to the N-type base region.

The other options are:

  1. BJT (Bipolar Junction Transistor): It consists of two P-N junctions forming three terminals: emitter, base, and collector.
  2. FET (Field-Effect Transistor): It consists of a gate, a source, and a drain, but its internal structure varies depending on the type (JFET, MOSFET).
  3. SCR (Silicon Controlled Rectifier): It consists of four layers of alternating P and N-type semiconductor material, forming three terminals: anode, cathode, and gate.
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