Lecture No# 6 Prepared by: Engr. Qurban Memon Incharge of Finally Project Lab.

LAB EXPERIMENT NO # 06 To understand reverse characteristics of zener diode by using Kit. Components: 1. BEE 422A Kit 2. Zener diode(12V or 10V) 3. dc supply 4. Load resistor (180Ω) 5. Few connecting leads 6. Volt meter (0 to 20dc) 7. Millimeter (0 to 200 mA) DISCUSSION: The first Zener diode was been invented by American Scientist Clerance Zener in 1956. The Zener diode has two terminals. The purpose of a voltage regulator is to maintain a constant voltage. 

The Zener diode work in both directions. Zener diodes are available for fixed (typically 5, 10 ,12V etc). Another name of Zener diode is breakdown diode. Zener diodes are widely used in electronic equipment. (computer, dc power supply etc).   A Zener diode is always connected in reverse.

Forward characteristic of zener diode

Forward characteristic of zener diode Reverse characteristic of zener diode

Types of break down diodes Zener diode Avalanche break down diode

Condition of zener diode in Reverse bias It means that the anode must be connected to the negative side of the voltage source and the cathode must be connected to the positive side. Reverse characteristic of zener diode

Condition of zener diode in forward bias: It means that the anode must be connected to the negative side of the voltage source and the cathode must be connected to the positive side. Forward characteristic of zener diode

The Zener diode has two states, namely; on and Off. On state: When reverse voltage across from a Zener diode the Vz is equal to or more than breakdown voltage Vz, the current increases very sharply. Under such condition, the Zener is said to be the “ON” State Suppose: If Vz=10v or > 10v Off state: When reverse voltage across from a Zener diode is less than Vz but greater than 0V, the Zener diode is in the “Off” state. Under such condition, the Zener diode can be represented by open switch. Suppose: If Vz<5v 0r 8v but > 0v

V-I characteristic of Zener diode