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Op-amp tutorial 2 : Features of inverting and non-inverting input and applications

Table of Contents:

Written By: 

Ajish Alfred
Features of inverting and non-inverting pins

The dependency of the output with the inverting and non-inverting pin can be simply explained as below,

 

If the inverting pin is high compared to other pin, the output is negative

 

If the non-inverting pin is high compared to other pin, the output is positive

 

This pecularity of the input pins are demonstrated in the following circuit. Let us take a 741 op-amp IC and keep the inverting pin at a high potential compared to the non-inverting pin.


5.jpgInverting pin high circuit
 
In the above circuit a 741 op-amp is used with two LEDs at its output. One LED (D1) has its anode connected to the output pin of op-amp and another LED (D2) has its cathode connected to the output pin of the op-amp. When the output voltage is positive D1 glows and when the output is negative, D2 glows.
 
Here inverting pin is connected to positive voltage (VCC) through a resistor R2, and the non-inverting pin is connected to GND through another resistor R1. Since the inverting input is having higher potential than the non-inverting pin, the output will be a negative voltage and D2 glows.
The image of the op amp circuit in Figure: 24 is shown below.
 
Image-25.jpg
Image of Inverting pin high circuit
 
If we make the connection in such a way that, the non-inverting pin is having a high voltage compared to the inverting pin, the output will be positive. The circuit for such a connection is shown below.
 

non-inverting_pin_high_circuit.jpg

Non-Inverting pin high circuit