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3.1 Diodes

Outcome 1 of 9 in domain 3 · Semiconductors and analog

Junction, rectification, Zener, LED, Schottky, flyback diode.

My targets

I declare:

Explain the PN junction and the threshold voltage, and measure it with the multimeter on a silicon diode, a Schottky and an LED.
Build a half-wave then a bridge rectifier, observe the output on the oscilloscope, and calculate the filter capacitor’s value.
Set a voltage with a Zener and its resistor, and say what the Zener dissipates.
Calculate an LED’s series resistor for a wanted current and explain why you never drive an LED from voltage alone.
Explain the flyback diode on a relay or motor and show on the oscilloscope the spike it removes.
Build a clipper and a clamper and observe what they do to a signal.
Build a diode-capacitor voltage doubler and measure its voltage unloaded then under load.
Diagnosis: a bridge rectifier with one dead diode, recognize the waveform and find the diode without desoldering.

Read

Kuphaldt, Lessons in Electric Circuits, volume III (Semiconductors), chapter 3: Diodes and rectifiers. "Introduction" gives the junction, the 0.7 V and the diode equation; "Meter check of a diode", why an ohmmeter on a diode is worth nothing; "Rectifier circuits", from half-wave to the bridge and its two drops, 1.4 V; "Inductor commutating circuits", the flyback diode, which he calls a commutating diode; "Zener diodes", "Schottky diodes" and "Light-emitting diodes", the rest of the RAS, series resistor included (a 1.6 V LED on 6 V, 220 Ω). "Clipper circuits", "Clamper circuits", "Voltage multipliers", targets 6 and 7. He writes in electron flow; see 1.1.