Diodes & Rectification — A/L Physics

What must I remember about Diodes & Rectification?

• Semiconductor Diode: Two-terminal p-n junction device designed to permit current flow essentially in one direction (forward bias) while presenting very high resistance in opposite direction (reverse bias).
• Diode Characteristic Curve: Forward characteristics show exponential conduction above knee/threshold voltage (Vk ≈ 0.7 V for Si, 0.3 V for Ge); Reverse characteristics show flat negligible leakage current Is until reverse breakdown voltage Vbr is reached.
• Half-Wave Rectification: Uses single diode to conduct only during positive half-cycles of AC input; Output frequency = Input frequency f; Maximum theoretical rectification efficiency η = 40.6%; Peak Inverse Voltage PIV = Vm.
• Full-Wave Rectification: 1) Center-Tapped Transformer (2 diodes); 2) Bridge Rectifier (4 diodes in diamond configuration); conducts during both half-cycles producing DC pulses; Output ripple frequency = 2f; Maximum theoretical efficiency η = 81.2%; Bridge Rectifier PIV = Vm.

Test yourself (1 minute)

1. Capacitor Smoothing Filter

   Shunt smoothing capacitor C connected in parallel across load resistor RL charges to peak voltage Vm and discharges slowly between peaks with time constant τ = RL * C; larger C produces smoother, flatter DC output with minimal ripple voltage.

2. Bridge Rectifier Conduction Path

   During positive half-cycle, diodes D1 and D3 conduct in series; during negative half-cycle, D2 and D4 conduct; current flows through load resistor RL in the IDENTICAL direction during both half-cycles.

3. Diode Protection

   A current-limiting resistor must always be connected in series with a diode to prevent catastrophic thermal destruction when conducting in forward bias.

Practise Diodes & Rectification questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 9: Electronics

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Where does Diodes & Rectification fit in the syllabus?

Unit 9.2 · Year 2 · Term 2