What is the significance of phase inversion in an operational amplifier?

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Discussion Overview

The discussion revolves around the concept of phase inversion in operational amplifiers, particularly focusing on the differences between inverting and non-inverting configurations. Participants explore the implications of phase inversion on output signals in relation to input signals, especially in the context of AC signals.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant expresses confusion about the significance of phase inversion in an inverting operational amplifier, questioning whether it makes a physical difference if the input signal starts from the positive or negative half cycle.
  • Another participant uses an analogy of a pulley to explain that when the input voltage rises, the output voltage lowers, indicating an inverse relationship.
  • Some participants highlight that while the input and output signals may appear similar in shape and frequency, an oscilloscope would reveal the phase difference, specifically noting that the output signal from the inverting input is 180 degrees out of phase with the input signal.
  • There is a suggestion that using a single-channel oscilloscope may not show the inversion clearly, as it would trigger the same way regardless of the phase of the input signal.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the significance of phase inversion, with some arguing that it is a critical distinction while others express uncertainty about its physical implications. The discussion remains unresolved regarding the practical effects of phase inversion on signal interpretation.

Contextual Notes

Participants mention the use of oscilloscopes to visualize phase differences, indicating that the discussion may depend on the specific measurement techniques employed. There are also references to the nature of AC signals, which may influence interpretations of phase relationships.

Hyperspace2
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In inverting operational amplifier when the signal is sent in -(minus) side then the signal is inverted at output. what does that mean? Whether it starts from positive half cycle or negative half cycle , it is an ac. I don't think it will make physical differences. I am so confused. Anyone can help. Advance thanks.
 
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http://en.wikipedia.org/wiki/Operational_amplifier_applications#Differential_amplifier

300px-Op-Amp_Differential_Amplifier.svg.png
 
Consider it a pulley.
If you pull the rope downwards then the other side goes upwards. And vice versa.

So it means when the input voltage rises, the output voltage will lower.
 
nivaOne said:
Consider it a pulley.
If you pull the rope downwards then the other side goes upwards. And vice versa.

So it means when the input voltage rises, the output voltage will lower.

I wasn't talking about that . I was talking about following phrases


"A signal fed into the + input (non-inverting) will produce an output signal that is in phase with the input signal. A signal fed into the - input (inverting) will produce an output signal that is 180 degrees out of phase with the input signal"

I was just trying to ask what is the differences between the input signal and the output signal that is 180 degrees out of phase of the input signal. I see them same ,because anyway they are the ac signal .
 
Hyperspace2 said:
I wasn't talking about that . I was talking about following phrases


"A signal fed into the + input (non-inverting) will produce an output signal that is in phase with the input signal. A signal fed into the - input (inverting) will produce an output signal that is 180 degrees out of phase with the input signal"

I was just trying to ask what is the differences between the input signal and the output signal that is 180 degrees out of phase of the input signal. I see them same ,because anyway they are the ac signal .

Hi,
If you look at each signal individually, you would only see signals with the same shape and frequency.
But if you would use an oscilloscope, you would see the difference.
 
If you look at your signals with a single channel oscilloscope then you will not see any 'inversion' - the scope will trigger the same way whatever phase of signal you give it and your "arc signal" will look the same, (or perhaps a different amplitude). You will only be aware of a phase difference if you show input signal (to trigger the scope with) on one channel and look at the two output signals, in turn, on the other channel. One will be in phase with the input and the other will be the other way up - in antiphase.
 

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