Help understanding this schematic

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Joined Jun 10, 2019

I was doing some reverse-engineering to a board and I came up with the circuit attached. I have depicted the current transformer with current source I1.
I want to understand how this circuit process the current transformer signal. What I can see is that the TVS diode D1 is for protection, followed by two Pi filters. But, what's the purpose of C5? I don't understand what happens after the burden resistor R1. There's a RC network at the non-inverting input of U1, does this cause a delay? At last, what's the function of the capacitor C7 which looks like it's in the positive feedback of U1. I think U2 and U3 non-inverting amplifiers for both positive and negative half cycles, right? I also see a DC offset of 1.65V added to the CT signal.
Last edited:


Joined Jan 23, 2018
Are the two inputs to the two opamps really tied like that? Everything else looks like a variation of an instrument amplifier circuit. And where does the mentioned current transformer enter into the discussion? With more information you can get better than a set of guesses, which is the best that can come from what is shown and stated so far.