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 times of its differential input. In simple terms, sensors give a low voltage output that cannot be easy to read, so an 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 give output without any input. To avoid noise signals we connect a variable resistor (POT-Potentiometer) in between +Offset and –Offset. Diagrams of the IC are shown below –
OPAMP LM 741 PINOUT
 OPAMP LM358 IC PINOUT
OPAMP WORKING
Op-amp has two inputs 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.
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 the same as the mathematical concept [+ multiply by number = number], [– multiply by number = – (number)].
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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Good, simple and useful information well explained.