1. Zener diode
2. Zener diode has sharp breakdown voltage than ordinary diode
3.
The zener diode is connected to a fluctuating voltage supply through a resistor R2 . The out put is taken across RL .
Working:
When ever the supply voltage increases beyond the breakdown voltage, the current through zener increases (and also through Rz).
Thus the voltage across Rz increases, by keeping the voltage drop across zener diode as a constant value. (This voltage drop across Rz is proportional to the input voltage)
Similarly, when supply voltage decreases beyond a certain value, the current through the zener diode decreases. Thus the voltage across Rz decreases, by keeping the voltage drop across zener diode as constant (Zener diode as a voltage regulator).