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Semiconductor Electronics

p-n junction, transistors, logic gates, communication

Key Concepts
  • Semiconductors: conductivity between conductors and insulators; increases with temperature
  • p-n junction diode: forward bias conducts, reverse bias blocks
  • Zener diode: operates in reverse breakdown — used as voltage regulator
  • Transistors (BJT): NPN or PNP; used as switches and amplifiers
  • Logic gates: AND, OR, NOT, NAND (universal), NOR (universal)
Important Formulae
Current in transistor I_E = I_B + I_C
Current gain (β) β = I_C / I_B
Current gain (α) α = I_C / I_E = β/(1+β)
Half-wave rectifier output V_dc = V_max / π
Full-wave rectifier output V_dc = 2V_max / π
Quick Tips
  • V_BE ≈ 0.7 V for Silicon, 0.3 V for Germanium in forward bias.
  • NAND and NOR gates are universal — any logic function can be built from them alone.
  • Intrinsic semiconductor: n_e = n_h; donor impurity increases electrons (n-type); acceptor increases holes (p-type).
Sample Practice Questions

  1. In an n-type semiconductor, majority charge carriers are:

    • Holes
    • Electrons
    • Protons
    • Ions
    Show answer

    Answer: Electrons

  2. Doping a pure semiconductor:

    • Decreases conductivity
    • Has no effect on conductivity
    • Increases its conductivity
    • Makes it an insulator
    Show answer

    Answer: Increases its conductivity

  3. The transistor is operated in saturation region when used as:

    • Amplifier
    • Oscillator
    • Switch
    • Rectifier
    Show answer

    Answer: Switch

  4. The output of an XOR gate is 1 when:

    • Both inputs are 0
    • Both inputs are 1
    • Inputs are different
    • All inputs are 1
    Show answer

    Answer: Inputs are different

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Practice Questions

Practice 20 randomly selected NEET questions on Semiconductor Electronics. Answers are revealed after each question.

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