Question

Name the device which is used as a voltage regulator.Draw the necessary circuit diagram and explain its working.

Answer 1

Zener Diode is used as a voltage regulator

When applied reverse voltage V is less than zener voltage V_z i.e., V < V_z, then zener diode does not conducts any current, and is said to be in OFF state. When V > V_z then zener diode conducts current at constant voltage V_z and is said to be in ON state.

Such zener diode is used in voltage stabilisation across a circuit.For this it is connected in parallel across the load resistor R_L in reverse bias. Suppose an unregulated d.c. input voltage V_in is applied to the zener diode of breakdown voltage V_z.When V_in < V_z zener diode does not conduct any current and hence input voltage appears across the load R_L.When V_in > V_z ,then the zener diode is in breakdown condition,and allows large reverse current to flow through it, keeping the voltage across it constant at V_z, which remains unaffected by value of load R_L .Thus, the output voltage across the zener diode is regulated voltage.