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</o:shapelayout></xml><![endif]--></head><body lang=FR-CA link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText><span lang=EN-CA>Following your wise suggestions I think the following circuit would<br>do a good job (precision & LSB kept wise).<br>On the DAC side, R5 will be in the feedback loop to keep 16 bits precision <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>and from loading the actual U19B opamp gain. (tested today in PSPICE)<br>Tested with a load going down to 3k !<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>The auto calibration (at final design step) will give the actual<br>offset to be adjusted for ADC/DAC correct tracking.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>As shown here a common +5VDC 0.2% reference (REF02BP)<br>will be used for both ADC & DAC for dual tracking.<br>No more trimmer..<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>One more question arises though..<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Should I use a gain 1 buffer between the R1/R2 node<br>and U16 AIN input ??<br>Even with C24 the ADC input has a track/hold circuit..<br>but the datasheet states that MAX11100 AIN input leakage current is 10uA worst case (40pf capacitance).. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>And.. adding another opamp in the ADC input chain could add possible offset problems.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Maybe that’s ok as it is so far..<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><br>BUT… As usual if you see something wrong please let me know..<br>Thanks.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>JP<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span style='mso-fareast-language:FR-CA'><img width=1081 height=901 id="Image_x0020_1" src="cid:image001.png@01D702D6.82FD3C50"></span><span lang=EN-CA><o:p></o:p></span></p></div></body></html>