1 © unitec new zealand apte 5601 &de4401 s emiconductors a tomic s tructure diodes

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APTE 5601 &DE4401

SEMICONDUCTORSATOMIC STRUCTURE

DIODES

Conductors, Semiconductors, Insulators

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Silicon Crystal Lattice- no free electrons

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N-type Silicon Doping –few free electrons

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P-type Silicon Doping – a few holes

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Summary of P & N Doping

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Combining to make P_N Junction

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P_N Zero Bias

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P_N Reverse Bias- wide depletion barrier

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P-N Forward Bias- thin depletion barrier

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P_N Diode Symbol & Characteristic I-V

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P-N Junction Diode Summary

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Diode Real vs Ideal Summary

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Small Signal Diodes

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Small Signal Diode V-I characteristic

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Small Signal Diode Summary

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Signal Diode Parameters

• Maximum Forward Current - else overheats

• Peak Inverse Voltage (PIV) - else breakdown

• Total Power Dissipation - in small fwd resistance

• Max Operating Temp – Junction Temp

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Apps- Arrays and Data Line Protection

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Diodes in Series – simple Voltage Regulator

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Freewheel Diode – protect from Inductor

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POWER Diode – much larger PN junction Basic RECTIFIER

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Rectifier - simplest

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Half-Wave Smoothing Capacitor

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Full Wave Rectifier – special transformer

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Full wave BRIDGE Rectifier

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Bridge – POS & NEG cycle conduction

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Bridge Rectifier Modules

• Cutoff corner = +, opposite = -, other two wires= AC input

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Bridge Smoothing Capacitor

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ZENER Diodes – Voltage Regulators

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Reminder - Voltage divider formula

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• The ratio of individual resistance to total resistance is the same as the ratio of individual voltage drop to total supply voltage in a voltage divider circuit. This is known as the voltage divider formula

Voltage Regulator – for variable loads

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ZENER series Resistor Calculations

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ZENERs in series

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Typical ZENER voltages available

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Using ZENERs to CLIP sine-waves

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Using Normal Diodes to Clip Sine-waves

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BIASED Clipping

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PhotoVoltaic (PV) diode cell

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PV BYPASS Diodes –prevent backflow from other shaded PVs or full battery

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LED Characteristics

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LED needs series resistor to limit current

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Series LED strings

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Driving LEDs with ICs

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Driving LEDs with Transistors

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Driving LEDs with Pulse Width Modulation

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OPTO Coupler - ISOLATION

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