OPAMP OR OPERATIONAL AMPLIFIER

In this tutorial section we will discuss about input and output signals of operational amplifier or OPAMP and OPAMP ICs which includes LM741 and LM358.

OPERATIONAL AMPLIFIER

Operational amplifier is a DC coupled high gain voltage amplifier with a differential input and whose output is several hundreds of time of its differential input. In simple, sensors give a low voltage output that cannot be easy to read, so operational amplifier is used to amplify the signal.

Two commonly used opamp are LM741 & LM358. Difference between LM358 & LM741 is, LM358 is newer and have two OP-AMP on chip while in 741 only one OP-AMP is present. Both the IC’s have 8 pins.

In op-amp LM741 Offset is used because any sensor can gives output without any input. To avoid noise signal we connect variable resister (POT-Potentiometer) in between +Offset and –Offset. Diagrams of the IC are shown below –

OPAMP LM 741 PINOUT

OpAmp LM 741 PINOUT
Op Amp LM 741 PINOUT

 OPAMP LM358 IC PINOUT

LM358 IC
OpAmp LM358 IC

OPAMP WORKING

Op-amp has two input namely inverting (–) and non-inverting (+) terminal and one output terminal.

NON INVERTING (+) INPUT

If the signal is passed through the non-inverting (+) terminal of the op-amp then there would be no change in output signal.

non inverting opamp

INVERTING (–) INPUT

If the signal is passed through the inverting (–) terminal of the op-amp then output signal will be inverted (just opposite). This is same as mathematics concept [+ multiply by number = number], [– multiply by number = – (number)].

inverting opamp

As op-amp has differential input, this means it compares the strength of the input signals at inverting (–) and non-inverting (+) terminal which one is greater will be considered as input.


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