Project Analog - November 2008 - (Page 17)

The same is true with Rule 3 — one must also consider the effect of input switching and sampling with respect to the voltage reference used by the data converter. For data converters with integrated references, this may not be an issue. But if you are using an external voltage reference to accurately bias your data converter, you can avoid op-amp afterthought by evaluating the need for a reference buffer early in your design process. The internal switching frequency common to successiveapproximation register (SAR) converters requires a constant charge to maintain the accuracy of the data converter. By choosing an amplifier with sufficient bandwidth and noise to drive the reference to an accurate final voltage within the acquisition time of the data converter, you can pat yourself on the back for once again not becoming a victim of op-amp afterthought. Contents Viewpoint Selecting the Proper Amplifier Using a Digital Potentiometer to Optimize a Photo Detection Circuit Resistor Networks in Critical Applications Analog news (a) (B) fiG 1 BaSic DiffErENcE amPlifiEr WiTh SEriES rESiSTaNcE aT ThE rEf PiN (moDElED By rrEf) crEaTES a volTaGE DiviDEr Error (a). PErcENT ouTPuT Error DuE To iNcrEaSiNG SEriES rESiSTaNcE aT rEf PiN for fiXED valuES of viN+ aND viN– (B). Microchip analog page Sample center microchipDIRECT Reference designs/ app notes Technical training fiG 2 BaSic DiffErENcE amPlifiEr WiTh BuffErED rEf PiN. 17 · PROjeCt ANAlOG · VOlUme 2 / NUmbeR 6 http://www.microchip.com http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - September 2008

Project Analog - September 2008 Contents Viewpoint About Project Analog Sponsor Selecting the Proper Amplifier for Strain Gauge Applications An Overview of Analog Sensor Conditioning Circuits Using a Digital Potentiometer to Optimize a Photo Detection Circuit Resistor Networks in Critical Applications Selecting the Right Op Amp Analog News Contact Microchip New Microchip Products Treelink MINDI™ Active Filter Designer Microchip Advanced Parts Selector (MAPS)

Project Analog - September 2008

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