American International University – Bangladesh (AIUB)
Faculty of Engineering
Analog Electronics – 2 (LAB)
Experiment No# 2
a. Use of LM 311 as precision comparator and window detector.
b. Triangular wave generator using 741 IC and LM 301
Theory:
The 311 comparator is an IC that has been designed and optimized for superior performance
in voltage-level detector applications. A comparator should be fast. The 311 is much faster
than the 741. The 311 is an excellent choice for a comparator because of its versatility. Its
output is designed not to bounce between V sat , but can be changed quite easily. Here
voltage may vary between levels of +15 V and – 15V, but VO is restrained between +5V and
0V, which are typical digital signal levels. Thus, 311 can be used for converting analog
voltage levels to digital voltage levels.
Exp. 2.1: Use of LM 311 as a precision comparator and window detector.
Objective:
The objective of this experiment is to use LM 311 as a zero crossing detector and window
detector.
Equipments required:
1. Power supply
2. Signal generator
3. Resistors
100 KΩ, 1 KΩ, 500 Ω
4. Oscilloscope
5. LM 311 (2)
Precision comparator or zero - crossing detector
Circuit Diagram:
V++ = 5V
Rf = 100 K
500
+15V
8
+
2
Ri = 1K
311
-
6
3
Ei
1
4
7
Strobe
(open)
-15V
Fig 1: Zero-crossing detector
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Procedure:
1. Connect the circuit according to the figure 1.
2. Apply an input voltage of 5 V (p-p) sinusoidal waves at Ei and observe the output.
3. Apply an input voltage of 5 V (p-p) square waves at Ei and observe the output.
Report:
1. Draw the input and output waveforms.
2. Discuss strobe terminal operation.
Window detector
The circuit is designed to monitor an input voltage and indicate when this voltage goes above
or below the prescribed limit. The output will be high when the input will fall between the
window ranges.
Circuit Diagram:
+15V
8
+
VHT = 5.5 V
2
311
7
3
V++ = 5V
4
1
500
-15V
- Ei +
1
4
2
7
+
311
3
VLT = 4.5 V
8
+15V
Fig. 2: Window Detector
Procedure:
1. Connect the circuit according to the figure 1.
2. Apply an input voltage of 5 V (p-p) sinusoidal waves at Ei and observe the output.
3. Apply an input voltage of 5 V (p-p) square waves at Ei and observe the output.
Report:
1. Draw the input and output waveforms.
2. Discuss the circuit operation.
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Exp. 2.2: Designing of Triangular wave generator with 741 IC and LM 301.
We can generate a basic bipolar triangular wave from the 741 integrator circuit, and a 301
comparator. An additional square wave signal is available at the output of the 301
comparator.
Equipments required:
1. Signal generator
2. Resistors
14 KΩ, 10 KΩ, 28 KΩ
3. Capacitance 0.05 μF
4. Oscilloscope
5. LM 301
6. Op Amp 741
Circuit Diagram
C= 0.05 uF
pR = 28K
+15 V
-15 V
Ri = 14K
741
+
-15 V
A
+
VA
-
+
R = 10K
301
+15 V
B
+
VB
-
Fig. 3: Triangular wave generator
Procedure:
1. Connect the circuit according to the figure 3.
2. Observe the wave shapes at the points A and B.
Report:
1. Draw the input and output waveforms at points A and B.
2. Find the frequency.
3. Connect a Diode in series with the resistor pR and observe the output wave shapes.
What is the difference between the two wave shapes?
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