Operational Amplifiers

An OP27 operational amplifier is used in this lab in order to show an inverting op-amp.

Gain = V(out) / V(in) = - (R2/R1). If R1 is equal R2, output voltage V(out) is equal negative of

input voltage V(in). An op-amp with gain = -2 is provided. Also a DMM in order to measure the

input and output voltage is used.

The measured resistance of R1 and R2 are: R1 = 2.1 k , R2 = 4.3 k So Gain = - 4.30/2.10 = -2.05

Figure 1: The schematic of a Real inverting Op-Amp

V(in)	V(out)
-3.49	3.46
-2.99	3.46
-2.49	3.46
-1.99	3.46
-1.49	3.01
-0.99	2
0	0
0.49	-1
0.996	-2
1.50	-3
1.99	-4.01
2.49	-4.23
2.99	-4.23
3.49	-4.23
3.99	-4.23

                        Data Table: 1

Figure 2: The Graph of Output Voltage vs Input Voltage

The saturated voltages are equal to the negative and positive power supplies.

V(in)	V(out)
-1.49	3.01
-0.99	2
0	0
0.49	-1
0.996	-2
1.50	-3
1.99	-4.01

                Data Table 2: Linear part 

According to the data table 2, gain is slope of the linear part of the graph output voltage vs input

voltage.           V(out) = - 2.0143 V(in) + 0.0039      ,     Gain = - 2.0143

percent error of gain = [(2.05 - 2.01)/(2.05)]* 100% = 1.95%

Figure 3: A Schematic of the inverting op-amp