Zener Diode and Voltage Regulators

Instituto Politecnico Nacional

High School of Computing

Analog Electronic

Practice 3

“Zener Diode and Voltage Regulators”

M en C. Ismael Cervantes de Anda

Team members:

Edgar Montes Gutierrez

Eder Ortega Ortuño

Adrian Tovar Rojo

Group 2CV7

Done on Septiembre 12th, 2013

To deliver on September 19th, 2013

Purpose:

➢ Analyze the breakdown voltage of a zener diode.

➢ Analyze key zener diode circuits

➢ Implement and analyze different integrated circuits that are used as controlled voltage sources.

➢ Implement and analyze the types of sources: fixed and variable.

Material:

➢ 1 tablet experimentation. (Proto Board)

➢ 2 to 3.3 V zener diodes 1/2 W

➢ Two zener diodes to 5.1 V 1/2 W

➢ Two zener diodes to 9.0 V 1/2 W

➢ Two resistors of 82 Ω to 2 W

➢ Two resistors of 33 Ω to 1 W

➢ Two resistors of 49 Ω to 1 W

➢ 4 resistance of 120 Ω ¼ W

➢ 2 Resistor 240 Ω ¼ W

➢ 2 Potentiometers of 10 k

➢ 2 Resistor 100 Ω to 10 W

➢ Four 0.1 uF capacitor to 50 V

➢ Two 10 uF electrolytic capacitor to 50 V

➢ 1 Regulator LM7805

➢ 1 Regulator LM7812

➢ 1 Regulator LM7905

➢ 1 Regulator LM7912

➢ 1 Regulator LM317

➢ 1 Regulator LM337

Equipment:

➢ 2 Digital Multimeters

➢ 1 Power Supply

➢ 2 Bits banana-alligator

➢ 2 Bits alligator-alligator

Theoretical Introduction:

A Zener Diode is an electronic component which can be used to make a very simple voltage regulator circuit. This circuit enables a fixed stable voltage to be taken from an unstable voltage source such as the battery bank of a renewable energy system which will fluctuate depending on the state of charge of the bank.

Zener Diode Voltage Regulator Circuit

Pictured above is a very simple voltage regulator circuit requiring just one zener diode (available from the REUK Shop) and one resistor. As long as the input voltage is a few volts more than the desired output voltage, the voltage across the zener diode will be stable.

As the input voltage increases the current through the Zener diode increases but the voltage drop remains constant - a feature of zener diodes. Therefore since the current in the circuit has increased the voltage drop across the resistor increases by an amount equal to the difference between the input voltage and the zener voltage of the diode.

Procedure:

1) Operating circuits zener

Assemble the following circuit for each of the diodes.

For the 3.3 V zener diode employing a resistance of 82 Ω and a resistance at Rs 33 Ω in Ro, vary the supply voltage as shown in the table and measure the voltage across the resistor R1 and record in the table.

For the 5.1 V zener diode employing a resistance of 56 Ω and a resistance at Rs 49 Ω in Ro, vary the supply voltage as shown in the table and measure the voltage across the resistor R1 and record in the table.

For the 9.0 V zener diode used Ω resistance at Rs 27 and a resistance of 82 Ω in Ro, vary the supply voltage as shown in the table and measure the voltage across the resistor R1 and record in the table.

Voltage Source V (V) Voltage resistance Ro

3.3 V 5.1 V 9.0 V

3.0 0.837 1.52 2.40

4.0 1.11 1.9 3.19

5.0 1.47 2.34 3.93

6.0 1.7 2.89 4.78

7.0 2.08 3.5 5.51

8.0 2.38 4.1 6.21

9.0 2.64 4.32 6.96

10.0 2.93 5.01 7.91

11.0 3.15 5.18 8.52

12.0 3.36 5.33 9.27

13.0 3.54 5.43 9.47

14.0 3.7 5.53 10.01

15.0 3.79 5.71 10.41

2) Positive fixed voltage regulator

Build the following circuit and varies the voltage of the power supply to each of the voltage regulators (LM7805 and LM7812).

Voltage Source VI (V) Voltage resistance Ro

LM7805 LM7812

3.0 6.4 mV 1.76 V

4.0 1.6 V 2.64 V

5.0 2.50 V 3.54 V

6.0 4.42 V 4.50 V

7.0 4.89 V 5.55 V

8.0 4.94 V 6.50

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