Zener Diode Presentation

This Presentation was made for a 2nd year 1st term course.

1. Presentation on Zener Diode Submitted by: Abidur Rahman 1509056 Electronics and Communication Engineering Pritom Mojumder 1509053 KHULNA UNIVERSITY of ENGINEERING & TECHNOLOGY

2. A diode is a two-terminal electronic component that conducts primarily in one direction. It blocks current in the opposite direction. This unidirectional behavior is called rectification Introduction 1

3. A  Zener diode  is a particular type of diode  that allows current to flow not only from its anode to its cathode, but also in the reverse direction, when the so-called "Zener voltage" is reached . Clarence Melvin Zener the American physicist invented Zener diode. Introduction 2

4. Figure: Zener diode Symbol Introduction Figure: Zener diode Package 3

5. pn Junction V o n type carrier concentration p type x Depletion Layer + + + + + + + + + + + + + + - - - - - - - - - - - - - - E field E field force on electrons E field force on holes How can we make a diode? 4

6. Construction of Zener Diode The depletion region formed in the diode is very thin, less than 1 µm . Now, even for a small reverse bias voltage of about 5 V , allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material. The Zener diode's operation depends on the heavy doping of its p-n junction. (<1 µm) 5

7. Important Features Zener diodes have a highly doped p-n junction . Normal diodes will also  break down  with a reverse voltage but the voltage and sharpness of the knee are not as well defined as for a Zener diode.  Zener diode can be operated in breakdown region . In the forward bias direction, the zener diode behaves like an ordinary silicon diode . 6

8. Graphical Representation 0.7v V I F Reverse Bias Forward Bias V BR 7

9. Application In a DC circuit, Zener diode can be used as a voltage regulator to regulate the voltage across small circuits. 8 The function of the regulator is to provide constant output voltage . Zener diode will continue to regulate the voltage until the diodes current falls below the minimum I z value in the reverse breakdown region.

10. Application Zener diode can be used to make a Waveform Clipper . Two Zener diodes facing each other in series will act to clip both halves of an input signal. 9 Waveform clippers can be used to not only reshape a signal, but also to prevent voltage spikes from affecting circuits that are connected to the power supply.

11. Application A Zener diode can be applied to a circuit with a resistor to act as a voltage shifter . This circuit lowers the output voltage by a quantity that is equal to the Zener diode's breakdown voltage. 10

12. Application Zener diodes are also used in surge protectors to limit transient voltage spikes . 11

13. Application Another application of the Zener diode is the use of noise caused by its avalanche breakdown in a random number generator . Figure: Avalanche noise curve 12

14. Summary Zener diodes are designed to operate at voltages greater than the breakdown voltage ( peak reverse voltage ). Zener diodes are manufactured with a specific breakdown (Zener) voltage . Zener diodes are packaged the same as P–N junction diodes . Zener diodes are used to stabilize or regulate voltage. 13

15. Thank You For Your Attention Any Question ?