ANALOGUE ELECTRONICS III LAB REPORT 1
TITLE: INTRODUCTION TO OP-AMPS
COURSE: TELECOMMUNCATION AND INFORMATION
ENGINEERING.
GROUP 12
NAMES REG NO
NELLY FRIDA OCHIENG ENE221-0157/2022
ELIUD OMONDI ENE221-0127/2022
KATHERIN NCHEKU NKINI ENE221-0111/2021
OBJECTIVE
To gain experience with 741 op-amp in several typical application
To discover some of the basic imitation of op-amp
REQUIEMENTS
i. Oscilloscope
ii. Dc power supply
iii. LM 741 type OP-AMP
iv. Resistors Series
v. 0.1 µF capacitance
vi. Function generator
INRODUCTION
Amplifier is electronic device that increases the voltage, current or power of a signal. There are
three different types of amplifiers
Summing amplifier
Differentiating amplifier
Difference amplifier
Integrating amplifier
Summing amplifier
A summing amplifier has two or more inputs, and its output voltage is proportional to the
negative of the algebraic sum of its input voltages. Operational amplifiers are not limited to a
single input signal. The junction of Rf and Rin, which is also the input of the op-amp is a virtual
ground.
Therefore, we can add a second input resistor or more without causing any interference
between the input signals. The current through Rf will match the composite of all of the input
current, forcing the output voltage to reflect the combination of all input voltages and their
individual coefficients. As a result, the
Intergrating Amplifier
To obtain an op amp integrator, feedback resistor is replaced with capacitor.
Since the input circuit element is a capacitor, the circuit will only experience input current in
response to change in input voltage. The faster and the larger the change in input voltage, the
greater the input current, therefore the greater the output voltage in response.
Since output voltage wil reflect the rate if change of the input, the circuit will perform
differentiation. The genera equation for the output voltage is:
Vout = -RC *dVin /dt
The d/dt notation indicate differentiation with respect to time
INTEGRATING AMPLIFIER
The feedback resistor is replaced with a capacitor. Therefore, any feedback current must be
based on change on output voltage. As feedback current flow, the capacitor will gain an electric
charge, which will change according to the cumulative effect of the output signal.
If input voltage is zero, no input current will flow. Therefore, no feedback current can flow and
the output voltage will remain constant. If the input voltage is constantly changing, the output
voltage at any instant will be the integral of all past input voltage values. For example, a bipolar
sine wave input will actually produce another sine wave as its output, at a phase of 90 0 from the
input sine wave
Vout = -Vin/RC + K
Where,
K-fixed constant
R- input resistance in ohms
C- feedback capacitance in farads
PROCEDURE
Summing amplifier
Using the diagram which was provided, Rf of 100kΩ and R1=R2=R3=100kΩ was used. Vcc was
set to 10V. 100Hz sinusoidal waveform with peak-to-peak magnitude of 2 volts as input was
applied. Gain of the circuit was measured. The channel of scope was used to verify that the
amplifier was indeed summing up the input signal. Input and output signals was drawn.
Difference amplifier
Using the diagram which was provided, R1=1kΩ and R2=10kΩ was used. Vcc was set to 10V.
100Hz sinusoidal waveform with peak-to-peak magnitude of 2 volts as input was applied. Gain
of the circuit was measured. Both channel of scope was used to verify that the amplifier was
indeed summing up the input signal. Input and output signals was drawn.
Integrator circuit
Using the diagram which was provided, Rin =10kΩ, Rf =100kΩ and C= 0.1µF was used. Vcc was
set to 10V. 100Hz square waveform with peak-to-peak magnitude of 2 volts as input was
applied. Gain of the circuit was measured. The channel of scope was used to verify that the
amplifier was indeed integrating the input signal. Input and output signals was drawn.
Differentiator amplifier
Using the diagram which was provided, Rs= 100kΩ, Rf=10kΩ and C=0.1µ was used. Vcc was set
to 10V. 100Hz triangular waveform with peak-to-peak magnitude of 2 volts as input was
applied. Gain of the circuit was measured. Both the channels of scope were used to verify that
the amplifier was indeed differentiating the input signal. Input and output signals was drawn.
DISCUSION
Summing amplifier
Summing amplifier
Integrator amplifier
Difference amplifier
Limitations of op-amp
Finite gain
While ideal op-amps are assumed to have infinite open-loop gain, real op-amps have limited
gain. This can affect the performance in high-gain applications.
Finite bandwidth
Op-amps have limited bandwidth, which means their gain decreases at higher frequencies. This
is due to their gain-bandwidth product (GBP), which is constant for a given op-amp.
Input offset voltage
A small offset voltage may be present between the input terminals, even when they are ideally
at the same potential. This can lead to errors in precision applications.
Input bias current
The input terminals of an op-amp require small bias currents for proper operation. These
currents can create voltage drops across external resistors, causing inaccuracies.
CONCLUSION
The experiment was successfully done using 741 op-amp and some of the limitation of the op-
amp was noted.
REFERENCE
1. Lecture notes
2. Laboratory manual
