<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{mso-style-priority:99;
mso-style-link:"Texte brut Car";
margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
p.MsoAcetate, li.MsoAcetate, div.MsoAcetate
{mso-style-priority:99;
mso-style-link:"Texte de bulles Car";
margin:0cm;
margin-bottom:.0001pt;
font-size:8.0pt;
font-family:"Tahoma","sans-serif";
mso-fareast-language:EN-US;}
span.TextebrutCar
{mso-style-name:"Texte brut Car";
mso-style-priority:99;
mso-style-link:"Texte brut";
font-family:"Calibri","sans-serif";}
span.TextedebullesCar
{mso-style-name:"Texte de bulles Car";
mso-style-priority:99;
mso-style-link:"Texte de bulles";
font-family:"Tahoma","sans-serif";}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=FR-CA link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText><span lang=EN-CA>Thank you for your kind help Roman..<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Because this project won't be a 'multi unit' to come<br>The actual cost for the final opamp choice is not an issue (for a reasonable cost though).<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>After reading the 3 suggested opamps datasheets,<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>my choice will probably be between <b>MCP606-I/P</b> or <b>OPA340PA</b><br>Hmmm.<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><o:p> </o:p></span></p><p class=MsoPlainText><span lang=FR style='mso-fareast-language:FR-CA'>-----Message d'origine-----<br>De : Synth-diy [mailto:synth-diy-bounces@synth-diy.org] De la part de Roman Sowa<br>Envoyé : 17 février 2021 03:12<br>À : Brian Willoughby; SYNTH DIY<br>Objet : Re: [sdiy] ADc & DAC voltage dividers.. fixed resistors values finally..</span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>All 3 opamps I listed are unity gain stable and cover full input span, and even beyond rails.<o:p></o:p></p><p class=MsoPlainText>I also wrote about RRO and RRIO opamps in earlier post and how to overcome this limitation.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Roman<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>W dniu 2021-02-17 o 08:53, Brian Willoughby pisze:<o:p></o:p></p><p class=MsoPlainText>> Yeah, one thing to look out for is that not all rail-to-rail op-amps support the full voltage on both input and output. Quite a lot of them are only rail-to-rail outputs, and assume that you'll be using some gain. Thus, a voltage follower is going to work very poorly with those select chips.<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Always check the data sheets carefully and thoroughly.<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Brian<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> On Feb 16, 2021, at 23:30, Roman Sowa wrote:<o:p></o:p></p><p class=MsoPlainText>>> None of them would work in this scenario.<o:p></o:p></p><p class=MsoPlainText>>> My humble suggestion is to try MCP606 as "good enough". It's a tad slow but if you plan to use it only for CV sampling at 1kHz, it's still fast as lighning.<o:p></o:p></p><p class=MsoPlainText>>> Or other interesting opamps: LT1637, OPA340 to mention just 2<o:p></o:p></p><p class=MsoPlainText>>><o:p> </o:p></p><p class=MsoPlainText>>> Roman<o:p></o:p></p><p class=MsoPlainText>>><o:p> </o:p></p><p class=MsoPlainText>>> W dniu 2021-02-16 o 21:50, Jean-Pierre Desrochers pisze:<o:p></o:p></p><p class=MsoPlainText>>>> So far the precision opamps I have on hands are:<o:p></o:p></p><p class=MsoPlainText>>>> OPA2277PA<o:p></o:p></p><p class=MsoPlainText>>>> OP177G<o:p></o:p></p><p class=MsoPlainText>>>> OP275G<o:p></o:p></p><p class=MsoPlainText>>>> LF412CP<o:p></o:p></p><p class=MsoPlainText>>>> I don't think they fit the requirements..<o:p></o:p></p><p class=MsoPlainText>>>> Any ideas for a good 16 bits ADC front end opamp ?<o:p></o:p></p><p class=MsoPlainText>>>><o:p> </o:p></p><p class=MsoPlainText>>>><o:p> </o:p></p><p class=MsoPlainText>>>> -----Message d'origine-----<o:p></o:p></p><p class=MsoPlainText>>>> De : Mike Bryant<o:p></o:p></p><p class=MsoPlainText>>>> Envoyé : 16 février 2021 14:52<o:p></o:p></p><p class=MsoPlainText>>>><o:p> </o:p></p><p class=MsoPlainText>>>>> But to me 5V rail to rail opamps will never reach 0 neither +5.0v at their output when these values show at the input..<o:p></o:p></p><p class=MsoPlainText>>>>> Close values but not the original ones.<o:p></o:p></p><p class=MsoPlainText>>>>> Or maybe I am wrong on that.<o:p></o:p></p><p class=MsoPlainText>>>> The ones for ADCs have FET output stages so they'll happily go all <o:p></o:p></p><p class=MsoPlainText>>>> the way to zero accurately and pretty near to the positive rail. <o:p></o:p></p><p class=MsoPlainText>>>> And many ADCs don't go all the way up to 5V anyway as they need some <o:p></o:p></p><p class=MsoPlainText>>>> headroom for the internal op-amp on the voltage reference<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> _______________________________________________<o:p></o:p></p><p class=MsoPlainText>> Synth-diy mailing list<o:p></o:p></p><p class=MsoPlainText>> <a href="mailto:Synth-diy@synth-diy.org"><span style='color:windowtext;text-decoration:none'>Synth-diy@synth-diy.org</span></a><o:p></o:p></p><p class=MsoPlainText>> <a href="http://synth-diy.org/mailman/listinfo/synth-diy"><span style='color:windowtext;text-decoration:none'>http://synth-diy.org/mailman/listinfo/synth-diy</span></a><o:p></o:p></p><p class=MsoPlainText>> Selling or trading? Use <a href="mailto:marketplace@synth-diy.org"><span style='color:windowtext;text-decoration:none'>marketplace@synth-diy.org</span></a><o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>_______________________________________________<o:p></o:p></p><p class=MsoPlainText>Synth-diy mailing list<o:p></o:p></p><p class=MsoPlainText><a href="mailto:Synth-diy@synth-diy.org"><span style='color:windowtext;text-decoration:none'>Synth-diy@synth-diy.org</span></a><o:p></o:p></p><p class=MsoPlainText><a href="http://synth-diy.org/mailman/listinfo/synth-diy"><span style='color:windowtext;text-decoration:none'>http://synth-diy.org/mailman/listinfo/synth-diy</span></a><o:p></o:p></p><p class=MsoPlainText>Selling or trading? Use <a href="mailto:marketplace@synth-diy.org"><span style='color:windowtext;text-decoration:none'>marketplace@synth-diy.org</span></a><o:p></o:p></p></div></body></html>