Science · Class 12
Electronic Devices
Learn Electronic Devices with notes, examples, and practice questions.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Semiconductors, p-n junction diode, rectification, and basic logic gates — application-focused Class 12 physics unit.
Semiconductors
- Intrinsic: pure Si/Ge; extrinsic: doped n-type (electrons) or p-type (holes)
- Forbidden energy gap small (~1 eV for Si)
- Conductivity increases with temperature (unlike metals)
Diode & Applications
Forward bias
p to +, n to −; low resistance
Reverse bias
Small leakage current
Rectifier
AC → DC using half/full wave
Logic Gates
- OR: Y=A+B
- AND: Y=A·B
- NOT: Y=Ā
- NAND/NOR universal gates
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Forward bias
Diode conducts heavily when:
- 1p-side higher potential than n
Answer
Forward biased
NAND truth
A=1,B=0 → output?
- 1AND=0, NOT→1
Answer
1
Key Points to Remember
- ✓ LED: forward biased p-n junction
- ✓ Solar cell: photovoltaic
- ✓ Zener: voltage regulation
Exam Tips
- • Draw I-V characteristic
- • Truth tables for logic
- • Know symbol for each gate
∑
Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Semiconductors & Diodes
- Forward bias:p to +, n to − ; low resistance
- Reverse bias:Small leakage current
- Rectifier:AC → DC (half/full wave)
Logic Gates
- OR:Y = A + B
- AND:Y = A·B
- NOT:Y = Ā
- NAND / NOR are universal gates
Practice MCQs — Electronic Devices
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
n-type semiconductor has majority: