Google Search

Wednesday, October 5, 2011

ZENER DIODE CHARACTERISTICS


ZENER DIODE CHARACTERISTICS

 AIM: -   a) To observe and draw the static characteristics of a zener diode
               b) To find the voltage regulation of a given zener diode

 APPARATUS: -
                                              Zener diode.
                                              Regulated Power Supply (0-30v).
                                              Voltmeter (0-20v)
                                               Ammeter (0-100mA)
                                               Resistor (1KOhm)
                                               Bread Board
                                               Connecting wires

                  
CIRCUIT DIAGRAM:-


STATIC CHARACTERISTICS:-

                                          



REGULATION CHARACTERISTICS:-
                              
                                             
Theory:-
              A zener diode is heavily doped p-n junction diode, specially made to operate in the break down region. A p-n junction diode normally does not conduct when reverse biased. But if the reverse bias is increased, at a particular voltage it starts conducting heavily. This voltage is called Break down Voltage. High current through the diode can permanently damage the device
            To avoid high current, we connect a resistor in series with zener diode. Once the diode starts conducting it maintains almost constant voltage across the terminals what ever may be the current through it, i.e., it has very low dynamic resistance. It is used in voltage regulators.

PROCEDURE:-

Static characteristics:-

1. Connections are made as per the circuit diagram.
2. The Regulated power supply voltage is increased in steps.
3. The zener current (lz), and the zener voltage (Vz.) are observed and then
     noted in the tabular form.
4. A graph is plotted between zener current (Iz) and zener voltage (Vz).

Regulation characteristics:-

1. The voltage regulation of any device is usually expressed as percentage regulation
2. The percentage regulation is given by the formula
                                 ((VNL-VFL)/VFL)X100
                                 VNL=Voltage across the diode, when no load is connected.
                                 VFL=Voltage across the diode, when load is connected.
3. Connection are made as per the circuit diagram
4. The load is placed in full load condition and the zener voltage (Vz), Zener current (lz), load current (IL) are measured.
5. The above step is repeated by decreasing the value of the load in steps.
6. All the readings are tabulated.
7. The percentage regulation is calculated using the above formula   


OBSERVATIONS:-

Static characteristics:-


            S.NO
          ZENER
      VOLTAGE(VZ)
       ZENER CURRENT(IZ)



   




Regulation characteristics:-


            S.N0
VNL(VOLTS)

 

VFL (VOLTS)
RL (KΏ)
% REGULATION






MODEL WAVEFORMS:-


                        




PRECAUTIONS:-
1.    The terminals of the zener diode should be properly identified
2.    While determined the load regulation, load should not be immediately shorted.
3.    Should be ensured that the applied voltages & currents do not exceed the ratings of the diode.

RESULT:-

a) Static characteristics of zener diode are obtained and drawn.
b) Percentage regulation of zener diode is calculated.

0 comments:

Post a Comment