Op Amp Inverting/Non-inverting terminal nomenclature

In summary, the terms inverting and non-inverting refer to the amplifier as a whole, not just the op-amp. Inverting amplifiers will invert the sign or phase of the applied voltage, while non-inverting amplifiers will not. Connecting the input voltage to the negative terminal results in an inverting amplifier, hence the name. The power supply rails serve as rigid limits for the amplifier and driving the input terminal more positive or negative will cause the output terminal's voltage to move towards the respective supply rail. This results in a reversal of sign, making the output appear inverted on an oscilloscope. Increasing the positive or negative input will cause the output to go up or down, respectively.
  • #1
gfd43tg
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Hello,

I am wondering why the inverting terminal is the negative terminal and the non-inverting terminal is the positive terminal by name?
 
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  • #2
The terms inverting/non-inverting refers to the AMPLIFIER as a whole, not the op-amp by itself. Inverting amplfiers (regardless of how they are are made) will invert the sign of the applied voltage (or, equivalently, invert the phase) , i.e. the gain will e.g be -10 meaning 1V in will results in MINUS ten volts out.

Now, if you want to an inverting amplfier using an op-amp you will find that you will have to connect the input voltage to the negative terminal. Hence the name.
 
  • #3
All pins must be kept at voltages that lie between the power supply "rails".
They're called "supply rails" because they are reminiscent of railroad tracks , ie rigid limits .
The amplifier can't go outside them. (well, there's newfangled specialty ones that can but let's stick to basics)

Driving the + terminal more positive than the - terminal causes the output terminal's voltage to move toward the positive supply rail.
Conversely,
Driving the - terminal more positive than the + terminal causes the output terminal's voltage to move toward the negative supply rail.

Do you notice the reversal of sign?

An AC signal that's had its sign reversed looks on an osciloscope (or graph paper ) to be upside down, ie inverted.

It's really that old-fashioned and simple.
 
  • #4
Increasing the + input makes the output go up
Increasing the - input makes the output go down
 
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  • #5
What meBigGuy said.
 

Related to Op Amp Inverting/Non-inverting terminal nomenclature

1. What is an op amp?

An op amp, short for operational amplifier, is an electronic circuit component that amplifies the difference between its two input terminals. It is commonly used in various electronic devices, such as audio amplifiers, filters, and sensors.

2. What is the difference between the inverting and non-inverting input terminals of an op amp?

The inverting input terminal is where the input signal is applied, while the non-inverting input terminal is used for providing a reference voltage. In an inverting op amp, the output signal is the inverse of the input signal, while in a non-inverting op amp, the output signal is in phase with the input signal.

3. Why are the inverting and non-inverting input terminals labeled with a minus and plus sign, respectively?

The minus sign on the inverting input terminal represents the fact that the input signal is being inverted, while the plus sign on the non-inverting input terminal represents the fact that the input signal is not being inverted. This labeling convention is used to differentiate between the two input terminals and their functions.

4. Can the inverting and non-inverting input terminals be swapped in an op amp circuit?

Yes, the inverting and non-inverting input terminals can be swapped in an op amp circuit, but it will change the output signal. In an inverting op amp, swapping the input terminals will result in a non-inverted output signal, and in a non-inverting op amp, swapping the input terminals will result in an inverted output signal.

5. Are there any other names for the inverting and non-inverting input terminals of an op amp?

Yes, the inverting input terminal is also known as the inverting input, while the non-inverting input terminal is also referred to as the non-inverting input. These terms are used interchangeably and mean the same thing.

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