Inverting Voltage Amplifier

We are introduced to a new element, operational amplifier. Operational amplifier is a kind of voltage controlled voltage source. Operational amplifiers are commonly used in circuits to implement mathematical operations. Today's lab shows one of the ways to use the operational amplifier, multiplication by a negative constant.

We went over some problems involving operational amplifier.

Inverting

Non-Inverting

The conclusion is that Rout = -R2/R1 * Rin

We did an experiment on inverting amplifier. Here is the setup:

We measured the resistance of the two resistors

The output voltage turns out to be approximately two times of the input voltage. The voltage is negative because the operational amplifier is connected to inverting voltage.

We applied different input voltages to get different output voltages. Here is a table of all the data we collected:

VIn (V)	Vout (V)
-3	4.21
-2.5	4.21
-2	4.22
-1.5	3.17
-1	2.11
-0.5	1.05
0	0
0.5	-1.04
1	-2.1
1.5	-3.16
2	-3.44
2.5	-3.44
3	-3.43
3.5	-3.43
4	-3.43

It saturates at -2V and 2V. There is a linear relation between the input voltage and output voltage between -2V and 2V.

We calculated the percent error of resistance and gain.

	Experimental	Theoretical	Percent Error
R1 (kΩ)	2.17	2.20	1.36%
R2 (kΩ)	4.64	4.70	1.28%
Gain	-2.11	-2.14	1.37%

Summary: Operational Amplifier works as a voltage controlled voltage source. When it is connected to inverting voltage, the output voltage has the opposite sign. By applying different resistance values, the ratio of input voltage and output voltage is different.