Voltage regulation with Zener diode By:Engr.Irshad Rahim Memon.

PRACTICAL # 10

Voltage regulation with Zener diode

By:Engr.Irshad Rahim Memon

OBJECTIVE Objective of this practical is to learn that

how a Zener diode regulates voltage

SOME CONCEPT REGARDING ZENER DIODE Zener diode is one of the types of diode

which was developed by scientist Zener Clarence. Zener diode is a heavily doped silicon PN junction device that is designed to operate in reverse breakdown region. In Zener diode two types of reverse breakdowns occur.

(i) Zener break down (ii) Avalanche breakdown

SYMBOL

DESCRIPTION CONTINUED… Zener breakdown: Occurs at low reverse voltage Occurs only in Zener diode  Avalanche breakdown: Occurs at sufficiently high reverse

voltage such that diode will be damaged  

Occurs in both rectifier and Zener diode

CONTINUED…. Due to heavy doping depletion region

becomes thin and there are enough charge carriers  (majority and minority) in P & N region, that’s why less voltage is required by Zener diode to operate in reverse breakdown region. When Zener diode reaches Zener break down voltage “Vz”, its voltage remains almost constant even though the current changes drastically as shown in the figure 01.

In other words it can also be said that when Zener diode is operating in Zener breakdown region, it acts as voltage regulator for specified range of reverse current.

ZENER CHARACTERISTIC CURVE

Figure 01: IV characteristic curve for Zener diode

DESCRIPTION CONTINUED… Due to characteristic of voltage

regulation, Zener diode equivalent circuit is consisting of a voltage source as shown in figure 02. Zener diode does not produce DC voltage, but constant voltage drop is represented by a constant DC voltage source.

FIG02

Figure 02: Schematic symbol of Zener diode and it equivalent circuit (a) ideal model (b) practical model

LITTLE MORE CONCEPT REGARDING ZENER CURVE

Figure 3.3

MAIN APPLICATION It is used as Voltage Regulator

ZENER DIODE WITH VARYING INPUT VOLTAGE

COMING TOWARDS OBJECTIVE NOW

REQUIRED APPARATUS DC Variable Source Diode Breadboard Multimeter Connecting Wire etc.

PROCEDURE Prepare a series circuit consisting of a

resistor, Zener diode and DC voltage source as shown in figure 4.

FIG04

FIG04 CIRCUIT ON MULTISM Using 20V DC Variable Source

FIG04 CIRCUIT ON MULTISM Using 10V DC Variable Source

OBSERVATION When input voltage is sufficiently increased

then voltage across Zener diode remains constant even though current is

changing w.r.t to input voltage. In Both Cases(Case1:Using 20V DC Variable

Source & Case2: Using 10V DC Variable Source) Output Voltage is 5.1V

That Shows Zener Diode Performs Regulation

ANY QUERY