University of Khartoum Faculty of Engineering Department of Electrical and Electronics Engineering Electronics Lab

Experiment No. (2) Rectifier Forms

Contents
Introduction: 3
Theory: 3
Objectives: 5
Equipment: 5
Method and Procedure: 5
Results: 6
Discussion of Results: 7
Conclusion: 9

Introduction:
In this experiment diodes were used to implement two commonly used rectifiers namely the half and full wave rectifiers to investigate the functions of diodes and of course to convert AC into DC and see what wave characteristics change and how they change. Theory:
A rectifier is an electrical device that converts Alternating current (AC), which continually reverses direction within each half a cycle, to direct current (DC) which flows in one direction only. This process of conversion from AC to DC is known as rectification. Rectifiers are a direct application of diodes. Because of the alternating nature of the input AC sine wave, the process of rectification alone produces a DC current which, although unidirectional, consists of pulses of current. Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC current (as would be produced by a battery). In these applications the output of the rectifier is smoothed by an electronic filter to produce a steady current.
The two types of rectification required in this experiment are:
Half wave rectification A diode is connected to an ac source and to a load resistor, RL, forming a half-wave rectifier. Keep in mind that all ground symbols represent the same point electrically.
When the sinusoidal input voltage (Vin) goes positive, the diode is forward-biased and conducts current through the load resistor, as shown in part (a). The current produces an output voltage across the load RL, which has the same shape as the positive half-cycle of the input voltage.
Part(a): the output voltage looks like the positive half of the input voltage.

Part(b): During the negative alternation of the input voltage, the current is 0, so the output voltage is also 0.

So the resulting output becomes:

Full wave rectification
The full wave rectifier is a configuration of diodes and other devices in such a way that the AC current is converted into DC in both half-cycles without loss of power. The full wave rectifier allows uni-directional current to flow during the entire 360 degree cycle whereas a half-wave rectifier allows current through the load only during one-half of the cycle. The result of full-wave rectification is an output voltage with a frequency twice the input frequency and that pulsates every half-cycle of the input, as shown in Fig. below.

The average value, which is the value measured on a dc voltmeter, for a full-wave rectified sinusoidal voltage is twice that of the half-wave, as shown in the following formula. Objectives:
To investigate the function of a diode.
To convert AC into DC.
To compare draw, and measure the DC output voltage of different type types of rectifiers.
Equipment:
AC power supply.
Oscilloscope.
Diode 1N4001.
Resistor 2.2K.
Circuit breadboard.
Capacitor 50u.
Method and Procedure:
Part (A)
The circuit shown to the right was set up with an AC source.
The Oscilloscope was connected to the rectifier output then the max and min value of the output voltage were noted.
The DC voltage (average) was calculated and the frequency of oscillation was determined.

Part (B)
The circuit shown to the right was set up. And an AC supply was connected to the input of the circuit. The oscilloscope was connected to the rectifier circuit output. Then the value of the maximum and minimum values of the output voltage were noted. Then the DC voltage(average) was calculated and the frequency of oscillation in the output waveform was noted.

Results:
Part
Max output V
Min output
V
Avg. voltage
V
Frequency
Hz
A
1.4