AC coupling of a precision rectifier

[Zaphappy]

After much pulling of hair I realized my circuit didn't work because my signal generator was capacitor coupled.

I need the measurement to be AC coupled OR reject any DC that the signal may be riding on. How can I accomplish this ?

 

[crutschow]

Add a non-inverting buffer amp (gain of +1) at the input to your precision rectifier circuit with a resistor to ground at the buffer input.
You can minimize part count by using a quad opamp for the three required amps.

 

[FvM]

I don't see a good way to save the circuit topology for AC coupled input, except for the rotten compromise of placing a low ohmic input resistor to ground.

"Zero drift" OPA745 is by the way no well suited for this kind of circuits due to it's extra overload recovery time.

A classical precision rectifier circuit with virtual ground at mid-supply would be my first approach.

 

[crutschow]

Yes, the added op amp I suggested won't work since you are using only a single supply.