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A/C signal processing circuit

Question asked by daroslav15 on Jan 2, 2012
Latest reply on Jan 5, 2012 by Gustavo.Castro

Hello,

I'm currenty designing A/C signal processing curcuit using AD op-amps. Could someone take a look at my circuit?

Design requirements:

 

Input signal:

bipolar source, not connected to GND, 2Vp-p

band: DS-10kHz,

source impedance: 50 ohms

 

Entire circuit must be powered from unipolar +5V source.

 

I was thinking about using 2 opamps for signal conditioning:

first opamp it's a simple double rail-to rail amplifier,

second would be theAD627 differential amplifier with single output, both can be powered from single supply.

AD627 has also Rail-to-Rail output.

My schem:

SCHEM.jpg

U1a and U1b are attenuating signal from 2Vpp to 0,8Vpp and are adding the offset of 2,5V. Minimum gain of ad627 is G=5 (without any resistor), so it's amplifying signal from 0,8Vpp to 4Vpp. At the same time AD627 adds offset to the signal and on the output it varies between 4,5V and 0,5V (4Vpp with 2,5V offset).

It's designed in this way, because I wanted to make almost full use of the ADC's Full Scale which is 0-5V. Output resistor and capacitor are creating simple anti-aliasing filter.

 

By the way: what is undersampling?

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