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Semiconductor Electronics: Materials, Devices and Simple Circuits

NCERT Class 12 Physics Chapter 14

Semiconductor Electronics for Class 12 Physics, JEE and NEET: energy bands, doping, the p-n junction, diodes and rectifiers, Zener diode and logic gates.

10 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET, unless a topic says otherwise

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Physics Part II (Class 12), Chapter 14 “Semiconductor Electronics: Materials, Devices and Simple Circuits”, reprint 2025-26.

Open the official NCERT chapter (PDF, 1.9 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Classification of metals, insulators and semiconductors

    How conductors, insulators and semiconductors differ, valence and conduction bands and band gaps.

    NCERT Sections 14.1–14.2 14 min read 4 solved examples 8 practice questions

  2. Intrinsic semiconductor

    Covalent bonds in Si and Ge, electron-hole pairs, hole current, carrier concentration and band diagram.

    NCERT Section 14.3 11 min read 4 solved examples 8 practice questions

  3. Extrinsic semiconductor

    Doping, n-type and p-type with donors and acceptors, majority and minority carriers, mass action law.

    NCERT Section 14.4 16 min read 5 solved examples 9 practice questions

  4. p-n junction

    How it forms, with a diagram, diffusion and drift currents, the depletion region and the barrier potential.

    NCERT Section 14.5 13 min read 5 solved examples 8 practice questions

  5. Semiconductor diode

    Forward and reverse bias, V-I characteristics, knee (threshold) and breakdown voltages, dynamic resistance.

    NCERT Section 14.6 14 min read 5 solved examples 9 practice questions

  6. Junction diode as a rectifier

    Half-wave and full-wave (centre-tap) rectifiers, output frequency, ripple and capacitor filters.

    NCERT Section 14.7 13 min read 5 solved examples 8 practice questions

  7. Zener diode: characteristic and voltage regulation

    Zener and avalanche breakdown, the symbol, the I-V characteristic and its circuit, and the Zener voltage regulator.

    JEE and NEET only 21 min read 5 solved examples 10 practice questions

  8. LED, photodiode and solar cell

    How each junction works with light, its bias, its I-V curve and how the band gap sets colour and cut-off.

    JEE and NEET only 18 min read 5 solved examples 9 practice questions

  9. Experiment: identifying a diode, LED, resistor and capacitor

    Identify a diode, LED, resistor and capacitor with a multimeter for JEE Main and NEET Unit 20: tests both ways, the capacitor’s kick and the colour code.

    JEE and NEET only 17 min read 5 solved examples 9 practice questions

  10. Logic gates

    OR, AND, NOT, NAND and NOR, with symbols, truth tables, Boolean expressions, De Morgan’s theorem and universal gates.

    JEE and NEET only 14 min read 5 solved examples 9 practice questions

Key formulas in this chapter

Metals, insulators and semiconductors

  • ρ = 1/σ
  • Eg = EC − EV

Intrinsic semiconductor

  • ne = nh = ni
  • I = Ie + Ih
  • σ = e(ne μe + nh μh)

Extrinsic semiconductor

  • ne ≫ nh (n-type)
  • nh ≫ ne (p-type)
  • ne nh = ni^2
  • σ = e(ne μe + nh μh)

p-n junction

  • Idiffusion = Idrift (equilibrium)
  • E ≈ V0/W

Semiconductor diode

  • Forward barrier = V0 − V
  • Reverse barrier = V0 + V
  • rd = ΔV/ΔI

Junction diode as a rectifier

  • fout = f (half-wave)
  • fout = 2f (full-wave)
  • τ = C RL

Zener diode

  • IZ(max) = PZ/VZ
  • RP = (V − VZ)VZ/PZ
  • IS = (Vin − VZ)/RS
  • IL = VZ/RL
  • IZ = IS − IL
  • rZ = ΔV/ΔI

LED, photodiode and solar cell

  • E = hν = hc/λ
  • E (eV) ≈ 1240/λ (nm)
  • λmax = hc/Eg
  • Pmax = Vm Im
  • FF = Pmax/(VOC ISC)

Experiment: identifying components

  • colour code: R = (10a + b) × 10c, with a, b and c the first three bands
  • tolerance: gold 5%, silver 10%, no fourth band 20%
  • charging kick of a capacitor: τ = RC
  • reverse-to-forward ratio = Rreverse/Rforward (also called the front-to-back ratio)

Logic gates

  • OR: Y = A + B
  • AND: Y = A·B
  • NOT: Y = NOT A
  • NAND: Y = NOT (A·B)
  • NOR: Y = NOT (A + B)
  • rows in a truth table: N = 2n
  • NOT (A·B) = (NOT A) + (NOT B)
  • NOT (A + B) = (NOT A)·(NOT B)

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