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THE 741 OPERATIONAL AMPLIFIER

V. Ryan © 2002-09

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The Operational Amplifier is probably the most versatile Integrated Circuit available. It is very cheap especially keeping in mind the fact that it contains several hundred components. The most common Op-Amp is the 741 and it is used in many circuits.

The OP AMP is a ‘Linear Amplifier’ with an amazing variety of uses. Its main purpose is to amplify (increase) a weak signal - a little like a Darlington Pair.

The OP-AMP has two inputs, INVERTING ( - ) and NON-INVERTING (+), and one output at pin 6.

   

The chip can be used in a circuit in two ways. If the voltage goes into pin two then it is known as an INVERTING AMPLIFIER.
If the voltage goes into pin three then the circuit becomes a NON-INVERTING AMPLIFIER.

   

The 741 integrated circuit looks like any other ‘chip’. However, it is a general purpose OP-AMP. You need only to know basic information about its operation and use. The diagram opposite shows the pins of the 741 OP-AMP. The important pins are 2, 3 and 6 because these represent inverting, non-inverting and voltage out. Notice the triangular diagram that represents an Op-Amp integrated circuit.

 

 

THE 741 IS USED IN TWO WAYS

 

   

1. An inverting amplifier. Leg two is the input and the output is always reversed.

In an inverting amplifier the voltage enters the 741 chip through leg two and comes out of the 741 chip at leg six. If the polarity is positive going into the chip, it negative by the time it comes out through leg six. The polarity has been ‘inverted’.

2. A non-inverting amplifier. Leg three is the input and the output is not reversed.

In a non-inverting amplifier the voltage enters the 741 chip through leg three and leaves the 741 chip through leg six. This time if it is positive going into the 741 then it is still positive coming out. Polarity remains the same.

   
 
   

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