DMT 121/3 – Electronic Devices
Laboratory Module
EXPERIMENT 3
DIODE AS RECTIFIER
1. OBJECTIVES
1.1
1.2
To understand the application of diode.
To demonstrate the characteristics of three different diode rectifier circuits: halfwave rectifier, center-tapped full-wave rectifier, and full-wave bridge rectifier.
2. INTRODUCTION
Assuming sine wave input with input frequency fin
2.1
Half-wave rectifier
VS ( peak )  VB
DC voltage output =

(sine wave input)
(3.1)
where: Vs ( peak ) is a transformer’s peak secondary voltage
V B is the peak voltage across 1k resistor
Output frequency
2.2
=
fin
Center-tapped full-wave rectifier
2VS ( peak )  VB 
Dc voltage output =
2 * fin
(3.4)
Full-wave bridge rectifier
2VS ( peak )  VB 
DC voltage output =

Output frequency =
2.4
(3.3)

Output frequency =
2.3
(3.2)
2 * fin
(sine wave input)
(3.5)
(3.6)
Percentage (%) error
In most practical analysis problems, a calculated value is considered to be
accurate enough if it is within ±10% of the actual measured value. The
percentage of error in a given calculation is determined using
X X'
% of error =
X
 100
(3.7)
where X = the measured value
X ' = the calculated value
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DMT 121/3 – Electronic Devices
Laboratory Module
3. COMPONENT AND EQUIPMENT
3.1
3.2
3.3
3.4
3.5
3.6
1 kΩ resistor
1N4001 silicon rectifier diodes (4 units)
Secondary center-tapped transformer (12 Vrms)
Oscilloscope
Multimeter
Breadboard
4. PROCEDURE
4.1 Half Wave Rectification:
4.1.1 Assemble the half wave rectifier circuit shown in Figure 3.1.
Figure 3.1: Schematic diagram of half-wave rectifier
(NOTE: Be very careful to make sure that connections to the 240V primary of the
transformer are properly protected. Note that neither of the transformer’s primary
leads is grounded, while the center-tapped secondary lead is not used in this
section.)
Determination of transformer’s peak secondary voltage [VS(peak)] and the
peak voltage [V0(peak)] across the 1 kΩ resistor:
4.1.3 Set oscilloscope to the following approximate settings:
4.1.2
Channels 1 & 2 :
Time base
:
10 V/division, dc coupling
5 ms/division
4.1.4 Apply 240 VAC (rms) to the transformer’s primary leads.
4.1.5 Connect one scope probe to the anode terminal of the 1N4001 diode
(point A).
4.1.6 Connect the other probe to the diode cathode terminal (point B).
4.1.7 Record your results in Table 3.1 and Table 3.2.
4.1.8 Next, we want to measure the dc voltage (VDC) across the 1 kΩ resistor.
4.1.9 Use your multimeter.
4.1.10 Record your result in Table 3.2.
4.1.11 Compare this result with that obtained from the equation for the average
or dc voltage of a half-wave rectifier (Equation 3.1).
4.1.12 Observe both waveforms. Then, turn off the power to the transformer.
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DMT 121/3 – Electronic Devices
Laboratory Module
4.2 Full-wave Rectification:
4.2.1 Then, assemble the center-tapped full-wave rectifier circuit shown in
Figure 3.2.
Figure 3.2: Schematic diagram of full-wave rectifier
(NOTE: Pay careful attention to the polarity of both diodes and the connections to
the 240V primary of the transformer. The center-tapped lead is grounded.)
Determination of transformer’s peak secondary voltage [VS(peak)] and the
peak voltage [V0(peak)] across the 1kΩ resistor:
4.2.3 Set your oscilloscope to the following approximate settings:
4.2.2
Channels 1 & 2 :
Time base
:
5 V/division, dc coupling
5 ms/division
Apply 240 VAC (rms) to the transformer’s primary leads.
Connect one probe to the anode terminal of the 1N4001 diode (point A)
Connect the other probe to one of the diode’s cathode terminals (point B).
Record your results in Table 3.1 and Table 3.2.
Then, using your multimeter, measure the dc voltage (VDC) across the 1
kΩ resistor.
4.2.9 Record your result in Table 3.2.
4.2.10 Compare this result with that obtained from the equation for the average
or dc voltage of a full-wave rectifier (Equation 3.3).
4.2.11 Observe both waveforms. Then, turn off the power to the transformer.
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
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DMT 121/3 – Electronic Devices
Laboratory Module
4.3 Full-wave Bridge Rectification:
4.3.1 Next, assemble the full-wave bridge rectifier circuit shown in Figure 3.3.
Figure 3.3: Schematic diagram of full-wave bridge rectifier
(NOTE: Pay careful attention to the polarity of all four diodes and the connections
to the 240V primary of the transformer. The center-tapped lead is grounded for
this section.)
4.3.2 Apply 240 VAC (rms) to the transformer’s primary leads.
4.3.3 Set the channel to dc coupling,
4.3.4 Connect the probe to the ungrounded lead of the 1kΩ (point A).
(NOTE: If everything is working properly, you should obtain the same full-wave
rectified waveform obtained in Step 4.2)
4.3.5
With oscilloscope, measure the peak voltage V0 (peak) across the 1 kΩ
resistor.
4.3.6 Record your result in Table 3.1 and Table 3.2.
4.3.7 Then, using your multimeter, measure the dc voltage (VDC) across the 1
kΩ resistor.
4.3.8 Record your result in Table 3.2.
4.3.9 Compare this result with that obtained in the equation for the average or
dc voltage of a full-wave bridge rectifier (Equation 3.5).
4.3.10 Observe both waveforms.
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DMT 121/3 – Electronic Devices
Laboratory Module
DMT 121/3 – ELECTRONIC DEVICES
ASSESSMENT FORM
NAME: __________________________________________ MATRIX NO: __________________
COURSE: _____________________________________ EXPERIMENT NO: _______________
RESULTS:
Table 3.1: Rectifier output waveform
Rectifier type
Input waveform
Half-wave
Full-wave
(center tap)
Full-wave
(bridge)
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Output waveform
DMT 121/3 – Electronic Devices
Laboratory Module
Table 3.2: Rectifier data
Measured
Rectifier
Type
VS (peak)
V0 (peak)
VDC
Half-wave
Full-wave
(center tap)
Full-wave
(bridge)
CALCULATION
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Expected VDC
% Error
DMT 121/3 – Electronic Devices
Laboratory Module
DISCUSSION
Explain in brief how full-wave rectification differs from half-wave rectification.
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DMT 121/3 – Electronic Devices
Laboratory Module
CONCLUSION
Based on actual and expected output, make your overall conclusion by referring to the
objective of this experiment.
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