Handy Dandy Little Circuits #30

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There are many different kinds of diodes . On these two pages I show circuits applications using the small signal diodes , the rectifier diodes and the zener diodes .

Small signal diodes are used to transform low current AC to DC , detect ( demodulate ) radio signals , multiply voltages, perform logic and a few other functions . A diode will not conduct until the forward voltage reaches a certain threshold point . For a silicon diode this voltage is about 0.6 volts and sligtly less for a germanium diode .

Power rectifier diodes are funtionally identical to the signal diodes and can handle much more current . Some are very large to absorb excess heat and may require a heat sink.

Zener diodes are designed to have a specific reverse voltage breakdown . It means that they can function like a switch . They also can be very large to absorb heat and may require a heat sink .

The Zener diode needs
a current limiting resitor (Rs)
to maintain its voltage regulating
point . The zener current is constant
regardless of load .

One method of obtaining
a split supply from a non
center tapped transformer
using zeners .

Zeners can be used to
raised the level of a voltage
regulator and obtain different
regulated voltage output .

Or Waveform Clipper

Zeners are used to rectify
an AC signal and clip its
level at the zener voltage
used . Different zener voltages
can be used rated below the AC
voltage .

When a high wattage zener
is not available or for economy
a small zener can be use with
a high power transistor to handle
the current as shown .