Introduction to the operational amplifier PDF

Preview

Summary

This lab for Introduction to the operational amplifier and build different circuits using it...

Description

Title: “Introduction to operational amplifier and build different circuits using it”

Introduction/Purpose: In this lab, we will study about the operational amplifier and will design the different circuits using op amp such as inverting amplifier, non-inverting amplifier, and inverting summing amplifier on the Multisim software. We will measure the output voltage for each circuit by varying the input voltages and will be calculating the gain for each circuit. An operational amplifier is 5 terminals with high input impedance, low output impedance, and high gain device. The 5 terminals of op-amp are namely inverting terminal, non-inverting terminal, positive and negative supply voltages, and output terminal as shown in figure 1.

Figure 1: Op amp schematic

Materials: 

Resistor (2.2k, 1k)



Capacitor (0.01µF)



Operational amplifier (Op amp 741)



DMM (digital multi-meter)



CRO (cathode ray oscilloscope)



DC Voltage supply

Methods:

 First of all, we will design a non-inverting amplifier as shown in figure 2, and will vary the input supply from 1V to 6V with an increment of 1V. +12V and –12V are connected to the 7 and 4 pins of the IC respectively. The output voltage is recorded in the table 1.

Figure 2: Non inverting amplifier schematic

 After that, we will design an inverting amplifier as shown in figure 3, and will vary the input supply from -1V to -6V with an increment of -1V. The output voltage is recorded in the table 2.

Figure 3: Inverting amplifier schematic

 After that, we will design an inverting summing amplifier as shown in figure 4, and will vary the input supply voltages from -1V to -6V with an increment of -1V. The output voltage is recorded in the table 3.

Figure 4: Inverting summing amplifier schematic

 Figure 3 circuit was modified by adding bypass capacitors of 0.01 µF between +12V and ground and –12V and ground as shown in figure 5. And the data was recorded in table 4.

Figure 5: Inverting amplifier schematic with by-pass capacitors



In the last part, the dc supply in figure 3 schematic was replaced with sine wave of frequency 500Hz, and amplitude 2VPP as shown in figure 6.

Figure 6: Inverting amplifier schematic with AC source

Data:  For non- inverting amplifier: Input V ¿ (V ) 1 2 3 4 5 6

Output V out (V ) 2.002 4.002 6.002 8.002 10.002 11.112

Measured gain

Calculated gain

Percent error

2 2 2 2 2 2

0.09% 0.05% 0.00% 0.00% 0.00% 8.00%

AV

2.002 2.001 2.000 2.000 2.000 1.852 Table 1: Non-inverting amplifier data

 For inverting amplifier: Input V ¿ (V ) -1

Output V out (V ) 1.002

Measured gain AV -1.002

Calculated gain

Percent error

-1

0.199%

2.002 3.002 4.002 5.002 6.002

-2 -3 -4 -5 -6

-1 -1 -1 -1 -1

-1.001 -1.000 -1.000 -1.000 -1.000

0.199% 0.00% 0.00% 0.00% 0.00%

Table 2: Inverting amplifier data

 For inverting summing amplifier: Inputs

Table 3:

V ¿1 (V )

Output

V ¿2 (V )

V ¿3 (V )

V out (V )

Measured gain

Calculated gain

Percent error

AV

-1 -2

-1 -2

-1 -2

−6.59

-6.59

−6.6

0.152%

−11.1

-5.55

−6.6

18.00%

-3

-3

-3

−11.1

-3.7

−6.6

43.9%

-4 -5

-4 -5

-4 -5

−11.1 −11.1

-2.775

57.9%

-2.22

−6.6 −6.6

-6

-6

-6

−11.1

-1.85

−6.6

71.9%

66.4%

Inverting summing amplifier data



Inverting amplifier with by-pass capacitor: Input V ¿ (V ) -1 -2 -3 -4 -5 -6

Output V out (V ) 1.00 2.00 3.00 4.00 5.00 6.00

Measured gain AV −1.00 −1.00 −1.00 −1.00 −1.00 −1.00

Calculated gain

Percent error

-1 -1 -1 -1 -1 -1

0.00% 0.00% 0.00% 0.00% 0.00% 0.00%

Table 4: Inverting amplifier data with by-pass capacitors

Results: For the non-inverting amplifier, the input is varied from 1V to 6V with 1V step, and the output voltage is recorded. The calculated and simulated results for voltage gain are approximately matched except the last value deviates from the calculated gain because of saturation level of op amp. Likewise, for the inverting amplifier, the input is varied from -1V to -6V with 1V step, and

the output voltage is recorded. The calculated and simulated results for voltage gain are approximately matched. For the summing inverting amplifier, the results till 2V are approximately matched, after that saturation level has been achieved. The calculated results for inverting amplifier with bypass capacitors are 100% matched with simulation results. The results for last part are shown in figure 12 and 13. Figure 12 shows the input and output waveform and peak to peak voltage of output wave comes out to be -2V. Figure 13 shows the input versus output graph, which is a straight line passing through the origin, and the slope of the line is 1.

Discussion and analysis: For non-inverting amplifier: The voltage gain for non-inverting amplifier is: A V =1+

Rf R¿

A V =1+

1 kΩ 1 kΩ

A V =2

For inverting amplifier: The voltage gain for inverting amplifier is: AV =

−R f R¿

AV =

−1 kΩ 1 kΩ

A V =−1 For inverting summing amplifier: A V =−

(

Rf R f Rf + + R¿ 1 R ¿2 R¿ 3

)

2.2 kΩ + ( 2.21 kΩkΩ + 2.2kΩ 1 kΩ ) 1 kΩ

A V =−

A V =−(2.2+2.2+2.2 ) A V =−6.6

Conclusions: The objective of this experiment was to study about the operational amplifiers, and design the different circuits such as inverting amplifier, non-inverting amplifier, and inverting summing amplifier on the Multisim software and record the data for inputs and output voltages. The calculated results for the voltage gain for each circuit are approximately matched with the simulation results. Hence the objective of this lab has achieved successfully, so we can mark it as a success.

Figures and graphs:

Figure 7: Non-inverting amplifier

Figure 8: Inverting amplifier

Figure 9: Inverting summing amplifier

Figure 10: Inverting amplifier with by-pass capacitors

Figure 11: Inverting amplifier with AC source

Figure 12: Input and output waveforms for figure 11 schematic

Figure 13:Vin vs. Vout graph...