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Class 12 Semiconductor Electronics worksheet
CBSE Physics. Intrinsic and doped semiconductors, carrier concentrations, p-n junctions, diodes, rectifiers. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
Silicon has an intrinsic carrier concentration of 1 × 10¹⁶ m⁻³. It is doped with 9 × 10²⁰ donor atoms per m³. The hole concentration is:
- 1.11 × 10¹¹ m⁻³
- 9 × 10²⁰ m⁻³
- 1 × 10¹⁶ m⁻³
- 1.11 × 10⁻⁵ m⁻³
Answer
(a) 1.11 × 10¹¹ m⁻³
nₑnₕ = nᵢ²; nₑ ≈ N_D
- 2.
Doping pure germanium with indium makes it:
- n-type, with electrons as majority carriers
- an insulator
- p-type, with holes as majority carriers
- p-type, with electrons as majority carriers
Answer
(c) p-type, with holes as majority carriers
indium is trivalent
- 3.
The input to a full-wave rectifier is 1000 Hz AC. The frequency of the output ripple is:
- 0 Hz
- 1000 Hz
- 2000 Hz
- 500 Hz
Answer
(c) 2000 Hz
both halves of each cycle give a pulse
Section B · short answer
- 4.
Pure silicon has nᵢ = 1 × 10¹⁶ m⁻³. It is doped with 6 × 10²³ pentavalent atoms per m³. Find the electron and hole concentrations, and name the type.
Answer
nₑ ≈ 6 × 10²³ m⁻³; nₕ = 1.67 × 10⁸ m⁻³; n-type
nₕ = nᵢ²/nₑ
- 5.
Silicon has 5 × 10²⁸ atoms per m³. It is doped with 1 atom of arsenic for every 10⁸ silicon atoms, and nᵢ = 1 × 10¹⁶ m⁻³. Find the number of donor atoms per m³ and the hole concentration.
Answer
5 × 10²⁰ m⁻³; 2 × 10¹¹ m⁻³
N_D = 5 × 10²⁸ ÷ 10⁸; nₕ = nᵢ²/N_D
Section C · long answer
- 6.
Silicon with nᵢ = 5 × 10¹⁵ m⁻³ is doped with 3 × 10²⁰ pentavalent atoms per m³. Find the majority and minority carrier concentrations, name the type, and say what happens to the band diagram.
Answer
electrons ≈ 3 × 10²⁰ m⁻³; holes = 8.33 × 10¹⁰ m⁻³; n-type; a donor level appears just below the conduction band
minority = nᵢ²/majority
Fresh sheets for your child
In the app, every Semiconductor Electronics sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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