# Circuit Explanation

Hey all,
This newb needs help understanding the posted circuit. Real quick, I'm going to post what I understand from left to right.
R53 and R62 = Voltage Divider
D2 = Clamping Diode (Clamping to 3.3V)
R45 = R1 in basic (R2/R1)Vin = Vout op amp formula

This is where I get stuck.
Let's call the node b4 R45 Vin. We would have [(Vin-Vref)/R45] = [(Vref - Vo)/R2] - however no R2. Instead, there's a diode that is in the off (depending on how you look at it) preventing any output from the first op-amp. Where then I guess the second OP Amp equation looks like Vo = [(Vin-Vref)/R45]. I am pretty sure I am missing some inverse logic in all of this, but regardless, I hope I got what I was trying to say across. Click Here for the Op-Amp datasheet. Any help would be greatly appreciated. Namely, what is that diode doing? What's the purpose of this circuit? Thank you.

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And when I say newb, I am referring to myself.

U10B work as clamping circuit. The output voltage can changer from 0 to 3V.
Higher voltage will be clamp.
Vout = Vin if Vin<3V, D4 is off and U10B is in positive saturation because inverting input voltage is smaller then non-inverting input.
And if Vin > 3V then Vout = 3V. Now D4 is ON and and closes the negative feedback loop. And non-inverting input is equal to inverting input voltage.
https://www.physicsforums.com/showpost.php?p=3866238&postcount=3

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What is this circuit used in? Do you know what Vfilter comes from?

I miss Altium by the way.

AlephZero