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Chapter: Electronic Devices - Special Semiconductor Devices

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Applications of zener diode

1.The Zener Diode Regulator 2. Zener-Controlled Output Switching 3. Zener Limiter 4. Zener Role in Power Supplies

Applications of zener diode


1.The Zener Diode Regulator



Figu re 4.8 Zener diode act as voltage regulator

 

The constant reverse voltage Vz of the zener diode makes it a valua ble component for the regulation of the output voltagge against both variations in the input volta ge from an unregulated power supply or variations in t he load resistance. The current through the ze ner will change to keep the voltage at within the limit s of the threshold of zener action and the maximum power it can dissipate.

 

2. Zener-Controlled Output Switching

This comparator application makes use of the properties of the zener diode to cause the output to switch between voltages determined by the zener diodes when the input voltage difference  changes sign. The output circuit amounts to a zener regulator which switches from one zener voltage to the other on a transition.


 

3. Zener Limiter

 

A single Zener diode can limit one side of a sinusoidal waveform to the zener voltage while clamping the other side to near zero. With two opposing zeners, the waveform can be limited to the zener voltage on both polarities.

 

Figure 4.9 Zener limiter

 

4. Zener Role in Power Supplies

 

The zener diode is widely used as a voltage regulator because of its capacity to maintain a constant voltage over a sizeable range of currents. It can be used as a single component across the output of a rectifier or incorporated into one of the variety of one-chip regulators Basically there are two type of regulations such as:

 

a) Line Regulation

 

 

In this type of regulation, series resistance and load resistance are fixed, only input voltage is changing. Output voltage remains the same as long as the input voltage is maintained above a

 

minimum value. 

Percentage of line regulation can be calculated by = 


 

Where V0 is the output voltage and VIN is the input voltage and ΔV0 is the change in output voltage for a particular change in input voltage ΔVIN.

 

b) Load Regulation

 

In this type of regulation, input voltage is fixed and the load resistance is varying. Output volt remains same, as long as the load resistance is maintained above a minimum value.


 


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