The Open University of Sri Lanka
Department of Electrical and Computer Engineering
ECX3510 Electrotechniques - TMA 3 - 2017/2018
In this 3rd Assignment we are learning a little about diodes and diode circuits. The diode, though
small and simple, has a very important role in electronics, therefore in all electronic devices around
you, as you will see while completing this assignment.
1. Describe briefly the behavioural characteristics of a semiconductor diode. Explain this
behaviour based on its structure. Describe briefly different materials that are used in the
manufacturing of diodes.
2. Diodes are classified into two classes according to their use and construction – rectifier (or
Power) diodes and signal diodes. Explain their differences in construction and in use.
3. We will look into some rectifier circuits. Sketch following diode circuits, and explain their
functioning.
a)
Half-wave rectifier
b)
Full-wave rectifier
c)
Bridge rectifier
4. There are many other uses for diodes. Describe the functioning of following diode circuits,
based on their circuits :
d)
Clipper circuit
e)
Clamper circuit
5. The Light Emitting Diode (LED) is one of the most widely used diode today.
f)
Describe briefly the reasons behind popularity of the LED.
g)
You are given 3 common LEDs of Red, Green and Blue colours. Devise a simple
circuit to light up all 3 diodes when they are connected in series.
h)
A simple method to safeguard the LEDs is to is add a ballast resistor. Why is it
necessary? Choose a suitable source EMF and a ballast resistor for the above circuit.
6. The source in the circuit provides am input e = 5sin 300t V. Sketch, relative to the input,
e
i)
The voltage across the diode, and the voltage across the
resistor separately, considering the diode to be fully ideal.
j)
The two voltages, when assuming the diode has a constant
forward biased voltage of 0.7 V.
This assignment may take you a little beyond your text book, and require searching additional
sources, but develop this skill, as it is an essential part of undergraduate studies.