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Operational
Amplifiers Explained (part 1)
Bill Naylor, Electronworks Ltd
This article explains the basics of how an
operational amplifier (op amp) works. You can use
one of our electronic kits to evaluate the theory.
If you have any suggestions for improving this
application note, please drop us a line at:
enquiries@electronworks.co.uk
The operational amplifier (op amp) is a simple
component in electronics, but one that can be used
in hundreds of complex circuit configurations. If
you understand it, you are well on your way to being
able to understand many electronic circuits.
An op amp is an amplifier – it makes voltages
larger. Most op amps only have 3 connections: a non
inverting input (+) an inverting input (-) and an
output. They also have 2 power supply connections.
The circuit symbol is shown in FIG 1
FIG 1
Let’s examine some of the circuit configurations of
an op amp. FIG 2 shows an op amp as a non inverting
amplifier.
FIG 2
The voltage at the output is determined by the
equation:
So with an input voltage of 1V, if we make R2 = 10kΩ
and R1 = 5kΩ then the output voltage is 3V. We have
built an amplifier with only 3 components.
Suppose we want to invert the signal. Then we use
the non inverting configuration as shown in FIG 3.
FIG 3
The voltage at the output is determined by the
equation:
Thus applying a signal of 1V at the input, if we
make R2 = 10kΩ and R1 = 5kΩ then the output voltage
is -2V.
Thus it can be seen that the op amp is an extremely
elegant solution to amplifying a voltage and these
components are used in circuits such as audio
amplifiers, CD players, MP3 players and test
equipment. Later articles will show that there are
many more reasons why an op amp should be used to
amplify signals.
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