Question

Describe briefly with the help of a circuit diagram how a zener diode works to obtain a constant dc voltage from the unregulated dc output of a rectifier ?

Answer 1

These electrons are responsible for the high current at the breakdown.

Voltage regulator converts an unregulated dc output of rectifier into a constant regulated dc voltage using Zener diode. The unregulated voltage is connected to the Zener diode through a series resistance R_S such that the Zener diode is reverse biased. If the input voltage increases, the current through R_S and Zener diode increases. Thus the voltage drop across R_S increases without any change in the voltage drop across Zener diode. This is because in the breakdown region, Zener voltage remain constant even though the current through Zener diode changes.

Similarly, if the input voltage decreases, the current through R_S and Zener diode decreases. The voltage drop across R_S decreases without any change in the voltage across the Zener diode.

Thus any change in input voltage results the change in voltage drop across R_S without any change in voltage across the Zener Diode.

Thus, Zener diode acts as a voltage regulator.