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Working of this OP-AMP circuit

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In this Application Note, Section 4.2 GFCI Fault Detection and Test, page 14, can someone tell me the working of the circuit.

enter image description here

Unable to understand it.
 

You read the application note, so what part do you not understand ?


Regards, Dana.
 

First opamp is peak detector with gain of -100. Second opamp is comparator with, for some unknown reason, a diode on the output.
 

Hi,

Same circuit as in your last thread.

Klaus
 

You read the application note, so what part do you not understand ?


Regards, Dana.
Thank you. In the second line of the paragraph, it is mentioned " A discharge path", can you tell me what is the discharge path? 2. Is the signal in GFCI+, an AC signal? 3. Why is there a diode in output of both the op-amps?
--- Updated ---

Hi,

Same circuit as in your last thread.

Klaus
Thank you. In the second line of the paragraph, it is mentioned " A discharge path", can you tell me what is the discharge path? 2. Is the signal in GFCI+, an AC signal? 3. Why is there a diode in output of both the op-amps?
--- Updated ---

First opamp is peak detector with gain of -100. Second opamp is comparator with, for some unknown reason, a diode on the output.
Thank you. In the second line of the paragraph, it is mentioned " A discharge path", can you tell me what is the discharge path? 2. Is the signal in GFCI+, an AC signal? 3. Why is there a diode in output of both the op-amps?
 


First OpAmp acting as a FW rectifier.

1686935384781.png


The discahrge path is for C3 back thru R59, R10, R14,.

GFCI - https://home.howstuffworks.com/question117.htm


Regards, Dana.
--- Updated ---

Something like this :

1686940762785.png



Regards, Dana.
 
Last edited:


The ap note seems to indicate, rightfully, its FW :

1686952882109.png

It uses the diode for one phase, the OpAmp as a sign changer for the other.


Regards, Dana.
 

The ap note seems to indicate, rightfully, its FW :



Regards, Dana.
Not with those component values. It's got a gain of 100 in the negative direction. A gain of 1 in the positive direction.

Rerun your simulation without the cap and see what the output looks like.
 

@barry

I completely misinterpreted that ap note, frankly got lazy, threw investigative
thoroughness out the window. Even I noticed imbalance in sign changer G,
eg. could not function as that, and then promptly forgot to go back and look
at it again. Thanks for hauling me up by the short hairs.

The sim does not seem to work with or w/o cap, makes no difference,
and sim output just looks odd.

It does, however, seem to indicate a simple peak detector from output view
with 10 uF. It just pumps up cap and the slow leakdown rate thru fdbk R
essentially holds the charge.


Regards, Dana.
 
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