Jitaditya Mondal Analog Electronics Circuit Lab

Experiment Number- 2(a) Study of Reverse characteristics of Zener diode

EC-394 and EE (EC)-391

Aim/Object:- To find the reverse breakdown voltage. To plot the reverse characteristics of Zener diode.

Title:-

Study of Reverse characteristics of Zener diode. Theory:- Zener diode is highly doped diode. If reverse voltage across Zener diode is increases, the highly electrostatic field spontaneous liberation of electron from the outer most shell of the semiconductor atom. This increases the no of free electrons but at the same time the voltage across the element falls. This phenomenon is known as Zener breakdown. The Zener breakdown is a phenomenon where after the certain voltage through current through Zener increases but the voltage across Zener remains constant. As the reverse voltage Zener is increased after the Zener breakdown, the current ca get to a high value so a current limiting resistance is connected in series. As show in the circuit diagram the circuit diagram of Zener diode is connected in reverse bias and it can be observed that before the Zener breakdown its characteristics is just like a normal diode before avalanche breakdown. Also Zener diode is forward bias like a normal p-n junction diode. Components:-

1. Zener Diode Trainer Kit. a. DC voltage regulator (0 to 15V). b. Source resistance (470). c. Load resistance (470). d. Voltmeter. e. Multimeters

2. Port Connecting Wires. 3. Zener Diode Kit Power Supply. 4. Zener diode.

Circuit Diagram:-

Jitaditya Mondal Analog Electronics Circuit Lab

Procedure:- 1. Make the connection as shown in the circuit diagram. 2. Make sure the Zener diode is connected reverse bias. 3. Increase the supply voltage and note down the corresponding values of voltage

and current across and through the diode recorded by the millimeters connected in parallel and series respectively.

4. Now plot the graph between reverse voltages and reverse current respectively. 5. Find the Zener breakdown voltage. 6. Find the resistance of Zener diode breakdown.

Required Graph:-

Experiment Result:-

Sl. No. Input Voltage Output Current 1 1.00V 2 2.00V 3 3.00V 4 4.00V 5 5.00V 6 6.00V 7 7.00V 8 8.00V 9 9.00V

10 10.00V 11 11.00V 12 12.00V 13 13.00V 14 14.00V

Precaution:-

1. The connection should be correct. 2. The supply voltage should not exceed 14 volts. 3. Separate point should be used for +Ve wires and Ve wires. 4. The series resistance must be connected to limit the Zener current. 5. The value of series resistance should be calculated properly keeping the Zener

breakdown voltage as the voltage across Zener and a maximum of 100mA current.

Jitaditya Mondal Analog Electronics Circuit Lab

Discussion:- 1. Zener diode is only used in reverse bias condition and its characteristics curve is a

lot sharper then avalanche breakdown curve so it can be used as a voltage. 2. The circuit demands much higher input voltage for providing voltage regulation

under wide variation in input voltage. 3. Output voltage stability gets affected under temperature variation. 4. The power handling capacity of Zener is quite less.