Lab Report # 01
Lab Report # 10To measure the voltage gain of an inverting
OP-AMPTheory:
Operational Amplifier (Op Amp or OA for short) is an analog
integrated circuit developed in 1965 by Mr. Robert Widlar at
Fairchild Semiconductors Laboratories. The beauty with this OA is,
we work with it mathematically or almost mathematically.
In terms of construction, OAs are based on transistors'
amplification (mostly FET but there are some built with BJT), and
each OA contains few tens or hundreds of them. However, OA is one
functional, complex unit block, and it has many particular
characteristics.
An OA has the following main characteristics:1. High Voltage
Gain, noted with Av, and having 103..109 magnitudes/levels2. High
input impedance; the ideal case is Zi --> ohms (read this as:
Input Impedance tends to reach infinite value)3. Wide Bandwidth4.
Low output impedance; Zo --> 0 ohm.OP-AMP as a Summing
Amplifier:
The basic summer is shown below in the diagram. It has a number
of inputs through which various voltages are applied that are
supposed to be summed up.
The summer works on the inverting amplifier principal. The
output voltage is equal to the algebraic sum of inputs applied with
negative sign. The negative sign indicates inversion.
The general diagram showing a summer with n inputs is shown
below.If we have each input connected to a different resistor than
others then we get a WEIGHTED SUMMER. The output of which is
totally determined on the values of input resistances.
CIRCUIT SCHEMATICS
Procedure: I connected the circuit according to the circuit
diagram shown above. A 10V power supply(dual) was provided to each
input through a potentiometers. Multimeters were then employed to
find out the values for the input and output voltage.
Observations and CalculationsV1V2VO
+6.26 V+2.32V-8.67V
+5.00V+3.86V-8.44V
-7.11V-4.10+11.21V
.
Epilogue
Cutting in short, an OP-AMP is a very handy and useful device.
It provides output voltage based on the input provided to it. It
can amplify even a dead signal to a whole new life. But this has
its own disadvantages. By this way it also enhances the noise
signals to very large extents. So we use feedback to counter this
(
