Download EE-0903368-Electronics Laboratory Experiment 3-Feb-2017

The University of Jordan
School of Engineering
Electrical Engineering Department
EE 368
Electronics Lab
Experiment 3
Diode Applications (2)
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Electrical Engineering Department
Experiment 3
Diode Applications (2)
Objectives
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To investigate how clipper circuit using diodes is working.
To investigate how clamper circuit utilizing a capacitor with diode is working.
To see how diodes could work in logical AND and OR gates.
Theory
In this experiment, we will study the other three diode applications which are:
1) Diode Clipper circuits: also called limiters, are used to clip (limit) off the positive or
negative part of an input signal. They can be used for different applications such as circuit
protection or waveform shaping. There are mainly three types of diode clippers: Positive,
Negative and dual clipper circuits.
The Positive Clipper circuit practically clips (limits) the output signal during the positive
half cycle of the input signal to a certain voltage (V) where the diode is forward biased, and
passes the entire input voltage during the negative half cycles of the input signal (the diode is
reversed biased).
The Negative Clipper circuit allows the positive half cycle of the input voltage to pass (the
diode is reversed biased) and clips the negative half cycle to a certain voltage (-V) where the
diode is forward biased.
The Dual diode clipper is a combination of positive and negative clipper circuits, where both
positive and negative half cycles of the input signal are clipped to (V) and (-V) respectively.
The output signals from the types of clipping circuits are shown in Figure 1.
Figure 1: Clipper circuit principle
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2) Diode Clamper circuits: also called DC restorers circuit, is used to add a DC level to an ac
signal. For example, when we want to get -5V to 0V voltage from a signal swings between
0V and 5V we can provide the proper DC offset by using a passive Clamper circuit. For the
clamping circuit to work properly, the period (T) of the input signal should be less than the
time constant ( = RC) of the circuit by a factor of 5 approximately (i.e.  >>T). This
condition is needed to avoid distorting the voltage across the capacitor during the input signal
period.
The output signal is simply the input signal shifted by the voltage across the capacitor which
could be positive or negative. The Positive Clamper circuit shifts the input signal upward
with an amount of the capacitor voltage while the Negative Clamper shifts the input signal
downward with an amount of the capacitor voltage. The positive or negative clamper circuits
with a bias (adding DC voltage to the circuit) will shift the output signal to upward or
downward respectively with an amount of the capacitor voltage plus the value of the DC
voltage. The output signals from the positive and the negative clamper circuits are shown in
Figure 2.
Figure 2: Clamper circuit principle
3) Diode logic circuits: is used to construct Boolean logic gates from diodes. Not all logical
functions can be implemented using diode, only the logical OR and logical AND functions
can be realized.
The OR logic circuit consists of two diodes; their Anodes are connected to the input voltage
sources while thier cathodes are joined to the output through pull-down resistor to ground as
shown in Figure 3. If the input voltage is high (high means logic 1), the according diode is
forward biased and a current passes through the diode to create high voltage drop across the
pull down resistor (the output). If the input voltage is low (low means logical 0) the
according diode is reversed biased and disconnects the input signal from the output.
Figure 3: 2-inputs, 1-output OR gate using diodes
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AND logic circuit consists of two input voltage sources that are connected to two diodes
cathodes. The diodes anodes are connected to an additional voltage source Vcc through pullup resistor as shown in Figure 4. If the input voltages are high (high means logic 1), the
diodes are revered biased and no current flows through the resistor, so high output voltage is
found. On the other hand, if the input voltage is low (low means logical 0), the diode is
forward biased and a current pass through the resistor making low output voltage drop.
VSupply
Figure 4: 2-inputs, 1-output OR gate using diodes
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Procedure
Equipments & Part List
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Oscilloscope.
Function Generator (FG).
Digital Multi-Meter (DMM).
Resistors of values (1k, 100k ) Ω.
Diode 1N4006.
Two Digital Multi-Meter
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DC power supply.
Project Breadboard.
Connection wires and coaxial cables
Capacitor of value 1 µF.
Bridge rectifier.
PART-A The Diode Clipper circuits
A-1 Positive Clipper circuit
1- Construct the circuit shown in Figure 5 (a) by using 1N4006 Silicon diode and R=1kΩ.
2- Switch ON the Function Generator:
a) Set the voltage to 8Vp-p.
b) Set the frequency to 100Hz.
c) Choose the sinusoidal shape.
3- Switch ON the Oscilloscope:
a) Connect CH1 to the function generator.
b) Connect CH2 to the diode.
c) Set the channel coupling of CH2 to DC coupling.
4- Sketch the waveform on the Oscilloscope screen on the respective grids in Table 1 in the
answer sheet and label the necessary voltages indicating the clipping voltage.
5- Comment on the output signal shown on CH2.
6- Switch OFF the Function Generator:
a) Insert DC power supply with polarity shown in Figure 5 (b) (Positive clipper with bias)
with V = 2V.
b) Switch ON the Function Generator and the DC supply.
c) Repeat step 4.
7- Comment on the output signal shown on the CH2.
8- When finished, switch OFF the DC power supply and the Function Generator.
(a)
(b)
Figure 5: Positive clipper, (a) without bias and (b) with bias
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A-2 Negative Clipper circuit
1- Construct the circuit shown in Figure 6 (a) by using 1N4006 Silicon diode and R=1kΩ.
2- Switch ON the Function Generator:
a) Set the voltage to 8Vp-p.
b) Set the frequency to 100Hz.
c) Choose the sinusoidal shape.
3- Switch ON the Oscilloscope:
a) Connect CH1 to the function generator.
b) Connect CH2 to the diode.
c) Set the channel coupling of CH2 to DC coupling.
4- Sketch the Oscilloscope screen on the respective grids in Table 2 in the answer sheet and label
the necessary voltages indicating the clipping voltage.
5- Comment on the output signal shown on the CH2.
6- Switch OFF the Function Generator:
a) Insert DC power supply with polarity shown in Figure 6 (b) (Negative clipper with bias)
with V = 2V.
b) Switch ON the Function Generator and the DC supply.
c) Repeat step 4.
7- Comment on the output signal shown on the CH2.
8- When finished, switch OFF the DC power supply and the Function Generator.
9- Explain the effects of using practically diode not ideal diode.
(a)
(b)
Figure 6: Negative clipper, (a) without bias and (b) with bias
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A-3 Dual Clipper circuit
1- Construct the circuit shown in Figure 7 (a) by using 1N4006 Silicon diode and R=1kΩ.
2- Switch ON the Function Generator:
a) Set the voltage to 8Vp-p.
b) Set the frequency to 100Hz.
c) Choose the sinusoidal shape.
3- Switch ON the Oscilloscope:
a) Connect CH1 to indicating the clipping voltage.
b) Connect CH2 to the diode.
c) Set the channel coupling of CH2 to DC coupling.
4- Sketch the Oscilloscope screen on the respective grids in Table 3 in the answer sheet and label
the necessary voltages indicating the clipping voltages.
5- Comment on the output signal shown on the CH2.
6- Switch OFF the Function Generator:
a) Insert two DC power supplies V1 = 2V and V2 = -2V as shown in Figure 7 (b). (To avoid
any problems and short circuits, connect the branch of D1 in series with V1 somewhere on
the breadboard, connect the other branch of D2 in series with V2 in another place, then
connect both branches in parallel).
b) Switch ON both DC supplies and the Function Generator
c) Repeat step 3.
7- Comment on the output signal shown on the CH2.
8- When finished, switch OFF the two DC power supplies and the Function Generator.
(a)
(b)
Figure 7: Dual clipper, (a) without bias and (b) with bias
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PART-B The Diode Clamper circuits
B1- Positive Clamper circuit
1- Construct the circuit shown in Figure 8 (a) by using 1N4006 Silicon diode, R = 100 kΩ and C
=1µF.
2- Switch ON the Function Generator:
a) Set the voltage to 8Vp-p.
b) Set the frequency to 100Hz.
c) Choose the sinusoidal shape.
3- Switch ON the Oscilloscope:
a) Connect CH1 to function generator.
b) Connect CH2 to the resistor.
c) Set the channel coupling of CH2 to DC coupling
4- Sketch the Oscilloscope screen on the respective grids in Table 4 in the answer sheet and label
the necessary voltages.
5- What is the difference between the input and the output signals?
6- Plot the voltage of the capacitor:
a) Connect CH2 parallel to the capacitor for the circuit shown in Figure 8 (a).
b) Disconnect CH1 (Why?).
c) Sketch the capacitor waveform on the respective grids in Table 4 in the sheet answer and
label the necessary voltages.
7- Compute mathematically the capacitor voltage for the circuit shown in Figure 8 (a), and
compare it with the practical results you have got in step 6.
8- Change the load resistor to R = 1kΩ:
a) What is the effect of using low load impedance in the clamper circuit?
b) Does the circuit still work as clamper? Explain.
c) Sketch the Oscilloscope screen on the respective grids in Table 4.
9- Switch OFF the Function Generator:
a) Insert DC power supply as shown in Figure 8 (b) (Positive Clamper with bias) with value
of V=2V.
b) Use R = 100 kΩ.
c) Switch ON the Function Generator and the DC supply.
d) Sketch the Oscilloscope screen on the respective grids in Table 4.
10- When finished, switch OFF the Function Generator and the DC power supply.
(a)
(b)
Figure 8: Positive Clamper, (a) without bias and (b) with bias
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11- Compute mathematically the capacitor voltage for the circuit shown in Figure 8 (b).
12- What is the effect of adding DC bias voltage to the positive clamper circuit?
B-2 Negative Clamper circuit
1- Construct the circuit shown in Figure 9 (a) by using 1N4006 Silicon diode, R = 100 kΩ and C
=1µF.
2- Switch ON the Function Generator:
a) Set the voltage to 8Vp-p.
b) Set the frequency to 100Hz.
c) Choose the sinusoidal shape.
3- Switch ON the Oscilloscope:
a) Connect CH1 to Function Generator.
b) Connect CH2 to the resistor.
c) Set the channel coupling of CH2 to DC coupling.
4- Sketch the Oscilloscope screen on the respective grids in Table 5 in the answer sheet and label
the necessary voltages.
5- What is the difference between the input and the output signals?
6- Plot the voltage of the capacitor:
a) Connect CH2 parallel to the capacitor for the circuit shown in Figure 9 (a).
b) Disconnect CH1 (Why?).
c) Sketch the capacitor waveform on the respective grids in Table 5 in the sheet answer and
label the necessary voltages.
7- Compute mathematically the capacitor voltage for the circuit shown in Figure 9 (a), and
compare it with the practical results you have got in step 6.
8- Switch OFF the Function Generator:
a) Insert DC power supply as shown in Figure 9 (b) (Negative Clamper with bias) with value
of V=2V.
b) Use R = 100 kΩ.
c) Switch ON the Function Generator and the DC supply.
d) Sketch the Oscilloscope screen on the respective grids in Table 5.
9- When finished, switch OFF the Function Generator and the DC power supply.
(a)
(b)
Figure 9: Negative Clamper, (a) without bias and (b) with bias
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10- Compute mathematically the capacitor voltage for the circuit shown in Figure 9 (b).
11- What is the effect of adding DC bias voltage onto the Negative Clamper circuit?
PART-C The Diode Logic circuits
C1- AND Gate circuit
1- Construct the circuit shown in Figure 10:
a) Set Vsupply = 5 volt
b) Use R=1KΩ.
2- Set the values of the two DC supplies V1 and V2 according to Table 6 on the answer sheet
and measure the output voltage using the DMM.
3- When finished, switch OFF all the instruments.
4- Verify your results by explaining what happens to the diodes at different input voltages.
5- What do we call the resistor ( R ) in the circuit shown in Figure 10?
Figure 10: And gate circuit
C2- OR Gate circuit
1- Construct the circuit shown in Figure 11:
a) Set Vsupply = 5 volt
b) Use R=1KΩ.
2- Set the values of the two DC supplies V1 and V2 according to Table 7 on the answer sheet and
measure the output voltage using the DMM.
3- When finished, switch OFF all the instruments.
4- Verify your results by explaining what happens to diodes at different input voltages.
5- What do we call the resistor ( R ) in the circuit shown in Figure 11?
Figure 11: OR gate circuit
PART-D Do It Yourself (DIY):
A] From Figure 12 below, for the input and output signals, answer the following questions:
Input Signal
Output Signal
Signal Shape
Amplitude
Frequency
DC Offset
Clamping Voltage
Figure 12
B] With the components in hands, design and construct a circuit that will shift the input signal as
shown in the following Figure 12.
Your circuit design goes here:
Note: Before leaving, you should show your results on the oscilloscope, exactly the same as
shown in Figure 12 above, to your lab instructor at lab and you will be graded right away.
The University of Jordan
School of Engineering
Electrical Engineering Department
Electronics Lab Report
0903368
Experiment No.: ______
Student Group #: ______
Experiment Title: _________________________________________
Students Name:
1) _________________________________________
2) _________________________________________
3) _________________________________________
4) _________________________________________
Report of Experiment 3
Diode Applications (2)
PART-A The Diode Clipper circuits
A-1 Positive Clipper circuit
Table 1
Step 4
VO-min = ………….
Step 6
VO-max = …………
VO-min = ………….
VO-max = …………
5- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
7- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
A-2 Negative Clipper circuit
Table 2
Step 4
VO-min = ………….
Step 6
VO-max = ………
VO-min = ………….
VO-max = …………
5- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
7- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
9- Explain the effects of using an ideal diode.
..............................................................................
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A-3 Dual Clipper circuit
Tabel 3
Step 4
VO-min = ………….
VO-max = …………..
Step 6
VO-min = ………….
VO-max = …………
5- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
7- Comment on the output signal shown on the CH2.
..............................................................................
..............................................................................
PART-B The Diode Clamper circuits
B1- Positive Clamper circuit
Table 4
Step 4
VO-min = …………. V O-max =………….
Step 6
Vr-pp = ……….
Step 8
Vc = . . . . . . . . . .
Step 9
VO-min = …………. V O-max =………….
5- What is the difference between the input and the output signals?
..............................................................................
..............................................................................
7- Compute mathematically the value of the capacitor voltage for the circuit shown in Figure 8
(a), and compare it with the practical results you have got in step 6.
..............................................................................
..............................................................................
8 (a) - What is the effect of using low load impedance in the clamper circuit?
..............................................................................
..............................................................................
8 (b)- Does the circuit still work as clamper? Explain.
..............................................................................
..............................................................................
11- Compute mathematically the value of the capacitor voltage for the circuit shown in Figure 8
(b).
..............................................................................
..............................................................................
12- What is the effect of adding DC bias voltage to the positive clamper circuit?
..............................................................................
..............................................................................
B-2 Negative Clamper circuit
Table 5
Step 4
VO-min = ……….
V O-max = ……….
Step 6
Vr-pp = ……….
Vc = . . . . . . . . . .
Step 8
VO-min = …………. V O-max =………….
5- What is the difference between the input and the output signals?
..............................................................................
..............................................................................
7- Compute mathematically the value of the capacitor voltage for the circuit shown in Figure 9
(a), then compare it with the practical results you got in step 6.
..............................................................................
..............................................................................
10- Compute mathematically the value of the capacitor voltage for the circuit shown in Figure 9
(b).
..............................................................................
..............................................................................
11- What is the effect of adding DC bias voltage to the negative clamper circuit?
..............................................................................
..............................................................................
PART-C The Diode Logic circuits
C1- AND Gate circuit
Table 6
V1(volt)
V2(volt)
0
0
0
5
5
0
5
5
Output
4- Verify your results by explaining what happen to diodes at different input voltages.
..............................................................................
..............................................................................
5- What do we call the resistor ( R ) in the circuit shown in Figure 10?
..............................................................................
..............................................................................
C2- OR Gate circuit
Table 7
V1 (volt)
V2 (volt)
0
0
0
5
5
0
5
5
Output
4- Verify your results by explaining what happen to diodes at different input voltages.
..............................................................................
..............................................................................
5- What do we call the resistor ( R ) in the circuit shown in Figure 11?
..............................................................................
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