OPERATION AMPLIFIER
Author Name: Vasilis Leandrou
OBJECTIVES
This report aims to:
- To explain an inverting operational amplifier circuit.
- To explain a non-inverting operational amplifier circuit.
- To find out the operational amplifier voltage follower.
BACKGROUND THEORY
In this experiment will be used the 741 operational amplifier, 3DC power supplies, an analog signal generator, a dual-trace oscilloscope and resistors (1ΜΩ, 100ΚΩ, 10ΚΩ, 4.7ΚΩ, 2.2ΚΩ, 1ΚΩ, 470Ω)
· The operation amplifier is an electronic circuit, increasingly important. It can be used as a circuit building block by focusing on its terminal behavior.
· Power supplies gives a source of power, rated as maximum voltage and current output
· The oscilloscope is an instrument that will display the variation of a voltage with time on a flat screen monitor.
EQUIPMENT and COMPONENTS USED
· Dual Trace Oscilloscope (Brand: HAMEG, Model: HM 203-6, Serial Number: 46/87 Z33418)
· Function generator (Model: TG 550)
· Power supply (GW GPS-3030PP, Serial Number: EG820606)
· 741 operational amplifier
· Resistors (1ΜΩ, 100ΚΩ, 10ΚΩ, 4.7ΚΩ, 2.2ΚΩ, 1ΚΩ, 470Ω)
EXPERIMENTAL METHOD
Part 1
An inverting amplifier circuit. The dual-trace oscilloscope was connected onto an operational amplifier and the signal generator was replaced with a dc power supply witch is verified that the inverting amplifier is a dc amplifier. The resistance of Rf was changed and the output voltage and the gain was measured (table 1).
The inverting amplifier voltage gain Av is equal with the feedback resistor divisible with the input resistor.
Av = -Rf / Rs
Part 2
A non inverting amplifier. The dual-trace oscilloscope was connected onto an operation amplifier and the signal generator was replaced with a dc power supply which is verified that is used as a non-inverting amplifier. The resistance of Rf was changed and the output voltage and the gain was measured (table 2).
The non-inverting amplifier voltage gain is determined by the equation:
Av= 1+ (Rf / Rs)
Part 3
Operational amplifier voltage follower. To find out the operational amplifier voltage follower, a circuit was connected with Vs = 5Vpk at 1 KHz. The output voltage V0 is measured. The procedure was repeated with Vs = 10Vdc and Vs = 2Vpk square wave.
OBSERVATIONS
Table 1 inverting amplifier
|
Rf(ohms) |
V0(volts) |
Av=V0/Vs |
Av=Rf/Rs |
different% |
|
471Ω |
50mV |
0.5 |
0.48 |
4% |
|
1ΚΩ |
100mV |
1 |
1.02 |
2% |
|
2.2ΚΩ |
225mV |
2.25 |
2.24 |
0.45% |
|
4.69ΚΩ |
480mV |
4.8 |
4.74 |
1.25% |
|
10.1ΚΩ |
1000mV |
10 |
10.32 |
3.2% |
|
94.5ΚΩ |
10.000mV |
100 |
101.7 |
1.7% |
Table 2 non-inverting amplifier
|
Rf(ohms) |
V0(volts) |
AV=V0/Vs |
Av=1+Rf/Rs |
different% |
|
471Ω |
150mV |
1.5 |
1.48 |
1.3% |
|
1ΚΩ |
200mV |
2 |
2.02 |
1% |
|
2.2ΚΩ |
340mV |
3.4 |
3.24 |
4.5% |
|
4.69ΚΩ |
600mV |
6 |
5.74 |
4.3% |
|
10.1ΚΩ |
1150mV |
11.5 |
11.32 |
1.56% |
|
94.5ΚΩ |
10000mV |
100 |
102.7 |
2.7% |
Data discussion
The operation amplifier is an electronic circuit, increasingly important. It can be used as a circuit building block by focusing on its terminal behavior. The circuit model of the operational amplifier requires the use of the depended source.
There are two basic configurations for operational amplifiers: the inverting amplifier and the non-inverting amplifier.
Operational amplifiers have countless open-loop levels which refer to those of an amplifier having no feedback resistance between output and input. Closed-loop characteristics are those of an amplifier having an external feedback resistor.
The resistors supply negative feedback whereby a part of the output voltage which is taken away from the input. Both amplifiers inverting and non-inverting use the main of negative feedback to control the overall voltage gain.
In the table 1 seeing that the values of the voltage gain using the formula (Av = V0 / Vs) and by using (Av = -Rf / Rs) is very small for example 0.5 and 0.48 at Rf = 471Ω.The same happens and on the non-inverting: the voltage gain is 1.5 and 1.48 when Rf=978Ω (table 2). The output voltage and the voltage gain is bigger using the non-inverting from the inverting amplifiers. For example when Rf = 471Ω on the inverting amplifier the V0=50mV and Av=0.5 and on the non-inverting V0=150mV and Av=1.5
The different between the two voltage gains are very small because there values are very closed of each other. Av= 0.5 and Av= 0.48 and the error different is 4% on the inverting amplifier (table 1). The same with the non-inverting amplifier, Av =1.5 and Av=1.48 and the error different is 1.3%
In the figure seeing that the two voltages is equal.
Error Analysis
To find the different of the voltage gain using Av= V0/Vs and Av=-Rf/ Rs on the inverting amplifier using the follow equation:
(Av= V0/Vs)-( Av=-Rf/ Rs) x 100% Av= V0/Vs
On the table 1 Av= V0/Vs= 0.5 and Av=-Rf/ Rs=0.48 The between them different is (0.5-0.48) / 0.5 x 100% = 4% different
To find the different of the voltage gain using Av= V0/Vs and Av=1+Rf/ Rs on the non- inverting amplifier using the follow equation:
(Av= V0/Vs)-(Av=1+Rf/ Rs) x 100% Av= V0/Vs
The different between the two voltage gains are very small because there values are very closed of each other. Av= 0.5 and Av= 0.48 and the error different is 4% on the inverting amplifier (table 1). The same with the non-inverting amplifier, Av =1.5 and Av=1.48 and the error different is 1.3%
RECOMMENDATIONS
The operation amplifier is an electronic circuit, increasingly important. It can be used as a circuit building block by focusing on its terminal behavior. The circuit model of the operational amplifier requires the use of the depended source.
There are two basic configurations for operational amplifiers: the inverting amplifier and the non-inverting amplifier.
Operational amplifiers have countless open-loop levels which refer to those of an amplifier having no feedback resistance between output and input. Closed-loop characteristics are those of an amplifier having an external feedback resistor.
The resistors supply negative feedback whereby a part of the output voltage which is taken away from the input. Both amplifiers inverting and non-inverting use the main of negative feedback to control the overall voltage gain.