Special-purpose diodes

Chapter 3.12 Special-purpose diodes

Lessons In Electric Circuits Volume III – Semiconductors Book
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Lessons In Electric Circuits Volume III – Semiconductors Book

  • 3.12. SPECIAL-PURPOSE DIODES143Figure 3.65:Zener diode clipper: v(1) input is clipped at waveform v(2).current.• A zener diode may function as a voltage regulator by acting as an accessory load, drawingmore current from the source if the voltage is too high, and less if it is too low.3.12Special-purpose diodes3.12.1Schottky diodesSchottky diodesare constructed of a metal-to-N junction rather than a P-N semiconductorjunction. Also known as hot-carrierdiodes, Schottky diodes are characterized by fast switchingtimes (low reverse-recovery time), low forward voltage drop (typically 0.25 to 0.4 volts for ametal-silicon junction), and low junction capacitance.The schematic symbol for a schottky diode is shown in Figure 152,3.66.AnodeCathodeFigure 3.66:Schottky diode schematic symbol.The forward voltage drop (VF ), reverse-recovery time (trr), and junction capacitance (CJ ) ofSchottky diodes are closer to ideal than the average “rectifying” diode. This makes them wellsuited for high-frequency applications. Unfortunately, though, Schottky diodes typically havelower forward current (IF ) and reverse voltage (VRRM and VDC) ratings than rectifying diodes