Page 2 – PN Junction Diode (Complete Theory + Derivation)
Foundation of Analog Electronics – Device Physics + V-I Characteristics + Current Equation
🔹 1️⃣ Formation of PN Junction
When P-type and N-type semiconductors are joined, electrons diffuse from N → P and holes from P → N.
This diffusion creates: ✔ Depletion Region ✔ Built-in Electric Field ✔ Barrier Potential
Barrier Potential:
Vbi = (kT/q) ln(NAND/ni²)
🔹 2️⃣ Biasing of Diode
Forward Bias
- Barrier reduces
- Current increases exponentially
Reverse Bias
- Barrier increases
- Only leakage current flows
🔹 3️⃣ Diode Current Equation (Very Important)
I = IS ( eV/ηVT − 1 )
Where:
- IS = Reverse saturation current
- VT = kT/q ≈ 26mV at 300K
- η = 1 (Ge), 2 (Si approx)
🔹 4️⃣ Small Signal Resistance
rd = ηVT / ID
Used in small signal model for amplifiers.
🔹 5️⃣ Temperature Effect
✔ IS doubles for every 10°C rise ✔ VT increases slightly ✔ Diode becomes more conductive
🔹 6️⃣ Important GATE Points
✔ Remember exponential relation ✔ At V >> VT, −1 can be neglected ✔ rd formula frequently asked ✔ Temperature effect important in numericals
Analog Electronics – PN Junction Complete Derivation | Shaktimatha Learning
.png)
No comments:
Post a Comment