# EECE-365 1 - UBC Electrical and Computer Engineering ```EECE-365
Department of Electrical and Computer Engineering
Experiment 2 – Diode Circuits
Introduction
This experiment demonstrates the operation of some of the circuits discussed in the lectures and introduces some
others. It also shows the non ideal nature of these circuits.
You will use a 60 Hz transformer with a center tapped 12.6 V output as the power source and initially use one of the
6.3 V sides only.
Students must pay special attention to the connections and measurements to avoid a short circuit occurrence and
damage to elements and measurement equipment.
Procedure
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It is a good practice to remove the power each time you change the circuit configuration.
It is also important that only one ground reference is used for the oscilloscope to avoid shorting the power
circuit throughout the oscilloscope frame.
Before connecting the electronic circuit to the transformer, make sure that you connected the high voltage
side of the transformer to the source. If you do not know, please ask. It is better to be safe than sorry. Then
use a voltmeter to check the secondary voltages of the transformer and identify the 6.3 V coils. A reversed
connection of the transformer can be very dangerous.
Using an AC voltmeter measure the secondary voltage. This is the RMS voltage and its value should be
close to the 6.3 V nominal value.
Construct each of the following circuits and connect the oscilloscope channels to measure vo(t) and vR(t).
The 1-Ω resistor connected in series with the load is included to allow a current signal into the oscilloscope.
If vR is the voltage across a 1 Ω resistor, then vR(t) equals the circuit current i(t).
Circuit 1. Half-wave rectifier.
Part 1.1
The circuit in Figure 1 corresponds to a half-wave rectifier feeding a 220 Ω resistive load.
1N4005
+
vo
-
220 ohms
1 ohm
-
vR +
i =v R
Figure 1. Half-wave rectifier feeding a resistive load
a. Sketch vs(t), vo(t) and i(t) indicating the maximum and minimum values.
b. Use a DC voltmeter to measure the average value of vo(t) and i(t). Name these VDC and IDC
1
EECE-365
Department of Electrical and Computer Engineering
Part 1.2
A resistive-inductive circuit can be obtained if a 1H inductor is connected in series with the 220 ohms
resistor as shown in Figure 2.
1N4005
1H
+
vo
-
220 ohms
1 ohm
-
vR +
i =vR
Figure 2. Half-wave rectifier feeding a resistive – inductive load
a. Sketch vo(t) and i(t) indicating the maximum and minimum values.
b. Use a DC voltmeter to measure the average value of vo(t) and i(t). Name these VDC and IDC
Part 1.3
Add a capacitor in parallel with the 220-Ω resistor to filter the output voltage.
Identify which is the positive terminal of the capacitor before connecting it.
A wrong connection of the capacitor may cause an explosion!
1N4005
1H
+
vo
-
+
33 &micro; F
-
vR +
Figure 3. Half-wave rectifier with output filter
a. Sketch vo(t) indicating the maximum and minimum values.
c. Use a DC voltmeter to measure the average value of vo(t). Name this voltage VDC
2
220 ohms
EECE-365
Department of Electrical and Computer Engineering
Part 1.4
Add a flywheel diode to the circuit shown in Figure 2 and observe the output voltage.
1N4005
+
vo
- 1 ohm
-
vR +
1H
220 ohms
i =vR
Figure 4. Half-wave rectifier with flywheel diode
b. Sketch vo(t) indicating the maximum and minimum values.
d. Use a DC voltmeter to measure the average value of vo(t). Name this voltage VDC
Circuit 2. Full-wave rectifier.
Part 2.1
Insert a third diode to add the output from the other end of the transformer winding to rectify the negative half of the
source voltage as shown in Figure 5.
1H
+
vo
-
220 ohms
1
-
vR +
Figure 5. Half-wave rectifier with flywheel diode