Are Non-inverting Opamps just like a transformers

[ren_zokuken01]

I've always thought that a Non-inverting configured Opamp simply takes the AC part of a signal and leaves out the DC, hence only needing for a +/-. Then reproduces the AC (with gain) and leaves out the DC. So the signals don't even have to be on the same ground as the supply voltage of the Opamps. The input can be from a completely different powered supply and it can be reproduced at by the Opamp as signals (with gain) much, much lower peak to peak Voltage range. So that's isolation, right? No common grounding needed.

Transformers also work the same way. Albeit the amplitude average of the input will be the average ground of the output, so not the same type of isolation as with Opamps. Also, Gyrators (active component Inductors), can be implemented by Opamps.

So why can't I reverse the inputs of the Opamp (while keeping the Non-inverting configuration) and expect that it will produce an inverted output? Is the positive input strictly only for push and the negative only pull, dictated by the fact that they are made out of transistor which needs proper biasing?

So are Opamps only like a transformer for only half (positive or negative) of an AC signal?

 

[Ramussons]

I've always thought that a Non-inverting configured Opamp simply takes the AC part of a signal and leaves out the DC, hence only needing for a +/-. ........ of an AC signal?

No, that's not true. The DC at the Non Inverting Input WILL appear at the output.

Vout = Vin * Amplification. AC or DC does not matter.

 

[ren_zokuken01]

OK, but am I right in the about the isolation thing? The peak-to-peak voltage of the input is isolated from the peak-to-peak output?

 

[Nigel Goodwin]

OK, but am I right in the about the isolation thing? The peak-to-peak voltage of the input is isolated from the peak-to-peak output?

No, there's no isolation either - an opamp is nothing like a transformer.

 

[alec_t]

No. The opamp itself doesn't provide any isolation. Coupling capacitors can be used to block any DC components of the input and output.

 

[AnalogKid]

A transformer is unique among all electronic components in that it a) "transforms" energy; and b) does so with complete galvanic isolation. Capacitors can provide the isolation, and can transfer energy (with losses), but the size needed is huge compared to a transformer moving the same amount of power. An opamp is neither of those things. A specialty "isolation amplifier" is just an opamp with a transformers or optocoupler built into the package, but a normal opamp is just an amplifier. You can couple to it with capacitors to remove the DC component of the signal, or a transformer to get isolation, but these are circuit techniques outside of the opamp itself.

ak

 

[ren_zokuken01]

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