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PHYS 3050 – Electronics I
Chapter 3. Diode Applications
Dr. Jinjun Shan, Associate Professor of Space Engineering
Department of Earth and Space Science and EngineeringRoom 255, Petrie Science and Engineering Building
Tel: 416-736 2100 ext. 33854Email: [email protected]
Homepage: http://www.yorku.ca/jjshan
Earth, Moon, Mars, and Beyond
Diode Applications 2
Introduction
A diode is a nonlinear element.
A diode has two terminals or two electrodes (hence di-ode), acts more like an on-off switch.
When it is “on”, it acts as a short circuit and passes all current.
When it is “off”, it acts as an open circuit and passes no current.
Diode Applications 3
Introduction
Diode has two terminals: plus and minus.
Forward bias – on
Reverse bias – off
A diode is also referred to as a rectifier.
It converts alternating current into direct current.
Diode Applications 4
Rectification
Ideal and Practical Diodes
Diode Applications 5
Rectification
Ideal and Practical Diodes
Diode Applications 6
Rectification
The most obvious differences between the ideal diode and and practical diode
Diode Applications 7
Rectification
Half-Wave Rectifier
Diode Applications 8
Rectification
ExampleThe input to the half-wave rectifier circuit if 120 VAC. If the resistance of diode is 20Ωand the load resistance is 100Ω. Find peak, DC and RMS load currents and the power dissipated in the load and the diode.
Diode Applications 9
Rectification
Full-Wave Rectifier
Diode Applications 10
Rectification
Rectifier Filters
Diode Applications 11
Rectification
Rectifier Filters
Diode Applications 12
Rectification
Rectifier Filters
Diode Applications 13
Rectification
Ripple Voltage Remaining After Filtering
Diode Applications 14
Rectification
Example: For full-wave rectifier, find V0
and Vr.
Diode Applications 15
Rectification
Example: We want to supply a DC voltage of 170 V to a load RL=1000 ohm. If the ripple voltage must be less than 3V, calculate the required capacitance? Assuming 120 VAC
at 60 Hz and full-wave rectifier.
Diode Applications 16
Rectification
Voltage Doubler
Diode Applications 17
Clipping and Clamping Circuits
Clipping
A typical function of a clipping circuit is to cut off part of an input waveform.
Diode Applications 18
Clipping and Clamping Circuits
Clipping and Limiters Clippers can be used as protection
circuits against voltage overshoot.
Diode Applications 19
Clipping and Clamping Circuits
Example: Battery backup system
Diode Applications 20
Clipping and Clamping Circuits
Clamping
Diode Applications 21
Clipping and Clamping Circuits
Clamping
Diode Applications 22
Clipping and Clamping Circuits
Clamping
Diode Applications 23
Zener Diode Voltage Regulation
We know capacitive filters in a power supply smooth the rectified voltage, the output voltage can still vary with changes in line voltage which can be due to a variety of causes.
If some circuits in electronic equipment must have an absolute steady voltage, we can use zener diode.
Diode Applications 24
Zener Diode Voltage Regulation
Since zener diodes are manufactured with a great variety of voltages (2-200 V), the need of any circuit for a constant voltage can be easily met.
Diode Applications 25
Zener Diode Voltage Regulation
Diode Applications 26
Zener Diode Voltage Regulation
Diode Applications 27
Zener Diode Voltage Regulation
Diode Applications 28
Zener Diode Voltage Regulation
Example:
It is desired to hold a load resistance RL at a constant voltage of 100 V as the input voltage varies between 120 V and 110 V. Find the best value of Rs to accomplish that purpose if Zener diode is used and RL
= 10 kΩ.
