chapter 2: diode applications - الصفحات الشخصية | الجامعة...

Chapter 2:

Diode Applications

Islamic University of Gaza

Dr. Talal Skaik

Copyright ©2009 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky

Zener Diodes

2

•A Zener diode is a type of diode that permits current

not only in the forward direction like a normal diode,

but also in the reverse direction if the voltage is larger

than the breakdown voltage known as "Zener voltage“

(VZ).

•Common Zener voltages are between 1.8 V and 200 V.

•Zener diode is used as regulator.

Dr. Talal Skaik 2014




Zener Diodes

3

Approximate equivalent circuits for the Zener diode in the three

possible regions of application.





Example 2.24

4

Determine the reference voltages

provided by the network which uses a white LED

(4V) to indicate power is on. What is the power

delivered to the LED and to the 6 V Zener diode.





Basic Zener Regulator

5

Determining the state

of the Zener diode.

Substituting the Zener equivalent

for the “on” situation

Remove Zener diode from network.

Calculate V across open circuit.

If V≥Vz , Zener diode is on.

If V<Vz, Zener diode is off.





Example 2.26

6

(a) For the Zener diode network, determine VL, VR, IZ and PZ.

(b) Repeat part (a) with RL=3 kΩ.





Example 2.26 - Solution

7

(a) determine VL, VR, IZ and PZ. (RL=1.2 kΩ)

V=8.73 V (<10)

IZ=0





Example 2.26 - Solution

8

(b) determine VL, VR, IZ and PZ. (RL=3 kΩ)





Voltage Doubler

9

This half-wave voltage doubler’s output can be calculated by:

Vout = VC2 = 2Vm

where Vm = peak secondary voltage of the transformer





Voltage Doubler

10

• Positive Half-Cycle

o D1 conducts

o D2 is switched off

o Capacitor C1 charges to Vm

• Negative Half-Cycle

o D1 is switched off

o D2 conducts

o Capacitor C2 charges to 2Vm

Vout = VC2 = 2Vm

(a) positive half-cycle; (b) negative half-cycle.





Voltage Doubler

11




Electronic Devices and Circuit Theory, 10/e Robert L. Boylestad and Louis Nashelsky 12

Practical Applications (AC to DC Converter)





Practical Applications Battery Charger

13





Practical Applications Battery Charger

14





Practical Applications - Polarity insurance

15

(a) Polarity protection for an expensive, sensitive piece of equipment; (b) correctly

applied polarity; (c) application of the wrong polarity.





Practical Applications - Polarity Detector

16

Polarity detector using diodes and LEDs.





Practical Applications – Exit sign using LEDS

17





Practical Applications – AC Regulator

18





Practical Applications – Square-Wave Generator

19


chapter 2: diode applications - الصفحات الشخصية | الجامعة...

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