EMT212/4
OP-AMP comparator basics
KOLEJ UNIVERSITI KEJURUTERAAN UTARA MALAYSIA
ANALOG ELECTRONICS 2
EMT 212/4
EXPERIMENT # 5
(OP-AMP COMPARATOR BASICS)
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NAME
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#
EXPERIMENT
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PROGRAMME
GROUP
DATE
TITLE
OP-AMP Basic Comparators
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
RTKennedy 04/05(edited NAI)
EMT212/4
OP-AMP comparator basics
OBJECTIVE
1.
To demonstrate the op-amp zero reference inverting comparator
2.
To demonstrate the op-amp negative reference inverting comparator
3.
To understand the op-amp negative reference non-inverting comparator
4.
To understand the op-amp comparator + positive output bounding
EQUIPMENTS & COMPONENTS
DC Power Supply, Function Generator, Oscilloscope, Voltmeter, LM 741 OP-AMP,
Breadboard, Resistors : 100 k (1), 10 k (1), Variable Resistor: 1 k (1), Zener Diode :
5.6V
INTRODUCTION
A comparator is a special type of op amp that is used to compare the voltages of the two
inputs. A basic comparator circuit is operated without a feedback loop.
When one input of the comparator is at a reference potential, the output will indicate whether
the unknown voltage at the other input is higher or lower than the reference.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
RTKennedy 04/05(edited NAI)
EMT212/4
1.
OP-AMP comparator basics
FIGURE 1 shows the schematic of zero reference inverting comparator. Apply a 5
kHz, 5V pk sinewave input signal to the circuit. Set both channels to gnd and
position the zero references using the vertical adjust. Record the Vout waveforms on
GRAPH 1. Set the oscilloscope to the X-Y mode and record the output-input voltage
transfer characteristic on GRAPH 2. Expand the x-axis and plot the voltage transfer
characteristic on GRAPH 3.
CH1
CH2
- 741
Vin
+
~
Vout
CH1 gnd
CH2 gnd
FIGURE 1
input
ZERO REFERENCE INVERTING COMPARATOR
GRAPH 1
voltage
0
4 marks
output
0
time
ZERO REF COMPARATOR CHARACTERISTIC
16
GRAPH 2
ZERO REF COMPARATOR CHARACTERISTIC
GRAPH 3
12
output voltage V
12
output voltage
16
8
4
0
4
8
12
8
4
0
4
8
12
16
16
5
4
3
2
1
0
1
2
3
4
5
input voltage
0.3
0.24
0.18
0.12
0.06
0
0.06
0.12
0.18
0.24
0.3
input voltage mV
2 marks
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
2 marks
RTKennedy 04/05(edited NAI)
EMT212/4
OP-AMP comparator basics
2.
FIGURE 2 shows the schematic of negative reference inverting comparator. Apply a
5 kHz, 5V pk sinewave input signal to the circuit. Set Vref , the DC reference, at -2 V by
adjusting RV. Then set both channels to gnd and position the zero references using the
vertical adjust. Record the Vout waveforms on GRAPH 4. Set the oscilloscope to the X-Y
mode and record the output-input voltage transfer characteristic on GRAPH 5. Expand the
X-axis and plot the voltage transfer characteristic on GRAPH 6.
-15V
10kΩ
CH1
(to +ve terminal
RV , 1kΩ
Vref
741
+
~
Vin
CH2
Vout
Vref
CH2 gnd
CH1 gnd
FIGURE 2
input
NEGATIVE REF INVERTING COMPARATOR
GRAPH 4
voltage
0
output
0
4 marks
time
16
NEGATIVE REF COMPARATOR CHARACTERISTIC
GRAPH 5
12
GRAPH 6
12
8
output voltage
output voltage
NEGATIVE REF COMPARATOR CHARACTERISTIC
16
4
0
4
8
12
8
4
0
4
8
12
16
16
5
4
3
2
1
0
1
2
3
4
5
input voltage
2.3
2.24
2.18
2.12
2.06
2
1.94
1.88
1.82
1.76
1.7
input voltage
2 marks
2 marks
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
RTKennedy 04/05(edited NAI)
EMT212/4
3.
OP-AMP comparator basics
FIGURE 3 shows the schematic of negative reference non-inverting comparator.
Apply a 5 kHz, 5V pk sinewave input signal to the circuit. Set Vref , the DC
reference, at -2 V by adjusting RV. Then set both channels to gnd and position the
zero references using the vertical adjust. Record the Vout waveforms on GRAPH 7.
Set the oscilloscope to the X-Y mode and record the output-input voltage transfer
characteristic on GRAPH 8. Expand the X-axis and plot the voltage transfer
characteristic on GRAPH 9.
-15V
10kΩ
CH1
Vin
~
(to –ve terminal)
RV,1kΩ
CH2
+
741
Vref
-
Vout
Vref
CH2 gnd
CH1 gnd
FIGURE 3
input
NEGATIVE REF NON-INVERTING COMPARATOR
output
voltage
GRAPH 7
4 marks
time
-VE REF NI COMPARATOR CHARACTERISTIC
16
GRAPH 8
12
-VE REF NI COMPARATOR CHARACTERISTIC
GRAPH 9
12
8
output voltage
output voltage
16
4
0
4
8
12
8
4
0
4
8
12
16
16
5
4
3
2
1
0
1
2
3
4
5
input voltage
2.3
2.24
2.18
2.12
2.06
2
1.94
1.88
1.82
1.76
1.7
input voltage
2 marks
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
2 marks
RTKennedy 04/05(edited NAI)
EMT212/4
4.
OP-AMP comparator basics
FIGURE 4 shows the schematic of op-amp comparator plus positive output
bounding. Apply a 5 kHz, 5V pk sinewave input signal to the circuit. Set both
channels to gnd and position the zero references using the vertical adjust. Record the
Vout waveforms on GRAPH 10. Then set the oscilloscope to the X-Y mode and
record the output-input voltage transfer characteristic on GRAPH 11.
DZ = 5.6V
5.6 V
100kΩ
CH1
~
Vin
CH2
- 741
R2
+
Vout
CH2 gnd
CH1 gnd
FIGURE 4
input
ZERO REF +VE BOUND INV COMPARATOR
output
voltage
GRAPH 10
4 marks
time
ZERO REF +VE BOUND INV COMP TF
8
output voltage
7
GRAPH 11
6
5
4
3
2
1
2 marks
0
1
5
4
3
2
1
0
1
2
3
4
5
input voltage
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
RTKennedy 04/05(edited NAI)
EMT212/4
OP-AMP comparator basics
QUESTIONS : BASIC COMPARATORS
mark
(2)
Q1
State the function of a comparator
Q2
State an alternative name for ZERO level comparators
(2)
Q3
What do GRAPHS 3, 6 & 9 indicate?
(2)
Q4
State the objective of output bounding
(2)
Q5
State an alternative name for OUTPUT BOUNDING
(2)
Q6
How does the comparator (no) hysteresis perform as a waveform generator (sine input)?
(2)
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
RTKennedy 04/05(edited NAI)