[SOLVED] Removing dc offset from Precision rectifier

[txbob]

The input for the precision rectifier has a 2.5v offset so does the output. To remove this offset I added a capacitor after the precision rectifier .My question is there any way I can remove the dc offset by adding a reference to my Precision rectifier this way I don’t have to use the capacitor? Your help is appreciated

 

[crutschow]

Why not use a full-wave precision rectifier such as this. It requires only 2 opamps, 1 diode, and 3 resistors, and generates a full-wave rectified signal with no DC offset using a single supply (with a single supply op amp of course). Here's an alternate circuit that uses only two resistors and has similar characteristics.

 

[txbob]

Thank you for the reply .Both the circuit as it is will not work with an input voltage which has 2.5v offset. If you don't agree please let me know. My second restiction is that I only have single supply operation is possible

 

[crutschow]

I think I now understand the problem (which you didn't state). Capacitive coupling of the rectified wave causes a DC offset of its own, since the cap output will go to the average value of the rectified signal. To avoid that, do the following:

1. Replace C1 with R3 (Remove R3 from ground).
2. Remove R10 from Vref and connect to ground.
3. Remove R1 from ground and connect to Vref.
4. Change R2 or R10 so they are both the same value.

This makes the output amp a direct-coupled differential stage which will cancel the common-mode 2.5V offset. Note that the op amp may not be able to pull the output completely to zero because of the current through R2 and R4. Higher resistor values for R2 and R4, and a low resistance output load to ground can help.

The differential gain is equal to R2 / R4.

 

[txbob]

Sorry for the delay
Thank you very much for your answer
I was little confused about the connection of reference
I am enclosing the diagram which worked the difference from your description was the location of reference. If you have any comments let me know
Ref desc got changed in new simulation