Experiment no.3

Experiment no:3

Zener diode

A zener diode is a special type of diode which allows current to flow in forward direction as normal, but it also allows it to flow in reverse direction, when the voltage above certain value- the brakedown voltage known as zener voltage

How it works?

The zener voltage of standard diode is high, but if a reverse current above that value is allowed to pass through then the diode is permanently damaged.

Zener diodes are designed so that their zener voltage is much lower

If zener diode is connected in forward direction it behaves exactly the same as a standard diode.example; small voltage drop 0.3 to 0.7 volts with current flowing through pretty much. In the reverse direction their is a small leakage current between ov and the zener voltage.

Example;  just tiny amount of current is able to flow. Then, when the reach the voltage(vz) suddenly current can flow freely through it

Uses of zener diodes. Zener diodes are specially used to regulate the voltage in circuits. Using resistors to ensure that the current passing through the zener diode is at leas 5 MA (0.005 amps)

Excersise

Components: 2 x resistors, 1 x 5V1 400mW zener diode (Zd)

For R= 100 ohms and RL= 100 ohms, Vs= 12V

I=V/R IL=5V/100 W = 50 MA

IS = IZ + IL, IS = 80 mA + 50 mA = 130 mA

R = V/I = 12-5 V/130 = 0.0538 ohms

What is the value of Vz? 5v

Vary Vs from 10 V to 15? 13.27V

What is the value of Vz?5.07V

What could this circuit be used for? Voltage regulator

Reverse the polarity of the zener diode

What is the value of Vz? Make short comment why you had that reading.

In the reverse direction is very small leakage current between 0.3 to 0.7 volts. In this circuit my meter reading is 0.3V and there was higher voltage drop so it means it needs higher voltage to push through, where as in the forward base. There is alot less voltage drop so it needs less voltage for current to go through

this is a picture of my experiment