Semiconductor Devices

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Based on resistivity (ρ), materials are classified as: 1. **Metals**: ρ = 10⁻² – 10⁻⁸ Ωm (high conductivity) 2. **Semiconductors**: ρ = 10⁻⁵ – 10⁶ Ωm (intermediate conductivity) 3. **Insulators**: ρ =

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**Valence Band**: Energy band formed by grouping energy levels of valence electrons (outermost orbit electrons). Present below conduction band. **Conduction Band**: Energy band formed by grouping ene

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**Metals**: Conduction and valence bands overlap → electrons easily move to conduction band → high conductivity **Semiconductors**: Small band gap (Eg ≈ 1 eV) → some electrons can jump to conduction

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**Intrinsic Semiconductor**: - Pure silicon or germanium - No impurities added - Electrons and holes always equal in number - Limited practical use due to high resistivity **Extrinsic Semiconductor**

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**n-type Semiconductor**: - Doped with pentavalent (5 valence electrons) elements - Dopants: Phosphorus (P), Arsenic (As), Antimony (Sb) - Extra electron becomes free → electrons are majority carriers

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**p-n Junction Formation**: - n-type and p-type regions created on same crystal - Electrons diffuse from n-region to p-region - Holes diffuse from p-region to n-region - Recombination occurs at juncti

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**Forward Bias** (p-side +ve, n-side -ve): - Reduces barrier potential - Large current flows (mA range) - Low resistance (10-30 Ω) - Knee voltage: ~0.7V (Si), ~0.3V (Ge) **Reverse Bias** (p-side -ve,

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**Given**: Vm = 10V, RL = 100Ω **For Half-Wave Rectifier**: DC Voltage: Vdc = Vm/π Vdc = 10V/π = 10/3.14 = 3.18V DC Current: Idc = Vdc/RL Idc = 3.18V/100Ω = 0.0318A = 31.8 mA **Note**: Half-wave r