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zener diode voltage regulator | zener diode Application note

This zener diode application note covers basic description on zener diode voltage regulator. The circuit diagram is mentioned.

The zener diode is normally used in reverse biased condition. The flow of current when diode is in reverse breakdown mode will not be destructive provided it is less than the certain value upto which diode does not overheated.

zener diode voltage regulator

Once the diode has breakdown mode, very little change in voltage across zener diode will result into change in current through the diode. Hence zener diode having known breakdown voltage can be used as reference voltage in reverse biased mode. It is used to regulate the voltages.

Voltage regulation is a measure of ability of circuit to maintain constant voltage output under variation either in input voltage or load current.

Figure depicts zener diode voltage regulator circuit and zener diode equivalent circuit. As shown, resistor Rs is used to limit reverse current through the diode to safe value. Both Vs and Rs are selected such that diode operates in breakdown region.

The series resistor Rs absorbs output voltage fluctuations to maintain voltage across load to constant value.
Is = (Vs-Vz)/Rs
Where in Is = Iz + IL

Zener diode maintains constant voltage across load as long as supply voltage is more than zener voltage.

Merits and demerits of zener voltage regulator

Zener diode voltage regulator is preferred over other voltage regulator types, as they are lighter, smaller and have long life. Moreover they are cheaper and simple to develop.

Following are the demerits of zener diode voltage regulator:
• Efficiency is low for high load currents.

• Output voltage slightly varies due to zener impedance(rz).

• Output voltage depends on breakdown voltage of zener diode and can not be selected as separate voltage.

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