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Advice on Implementing a Precision Full Wave Rectifier

Question asked by 1949live on Apr 8, 2016
Latest reply on Jun 28, 2016 by Emman.A

Hi - the attached AD paper describes building a precision full wave rectifier with a difference amp such as the AD8277.  I like this solution as it does not have the diodes typical of such a configuration which can lead to anomalies in the output, which this application cannot tolerate.  I have three questions regarding this:

 

1. There are no starting or recommended values for the resistors in Figure 3.  Can anyone provide me with same?

2. The difference amp allows me to implement an output offset using the Ref pin, which is important in this application (about 100mV positive for zero input).  Will using the Ref input cause any anomalous behavior in this application?

3. The input to this circuit comes off a divider network across an AC line, so by definition the source impedance is a few hundred K which will result in a high impedance input.  Will this setup tolerate such or do I need to buffer the input between the AC input dividers and the full wave rectifier circuit?

 

You can probably tell I am not an analog expert, and hence looking for some guidance from the community.  Thanks.

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