The following addresses the moderately important issue re data sheet reliability and vendor reliability. >>> TL072 are not unity gain stable, despite what some >>> sources claim. >> Hmm - this looks wrong. =A0I've been using TL07x as unity gain buffers >> for decades now. >> Just looking now: TI's data sheet >> says that the chips >> are unity-gain stable. =A0See page 9 of the PDF file I referenced above. > Yes, that's why I say "despite what some sources claim". =A0I have seen t= hese > things oscillate in some cases. =A0Maybe those weren't genuine TI parts. Digikey list only TI, ST and Diodes Inc parts. all give information on unity gain operation. This seems to be part of the formal TL072 specification. It would SEEM that *any reputable* TL072 part should work in this mode. ie datasheet says so, assume it's true. > If you allow your purchasing people to pick where they > get these amps from and who makes them, you'd be > better off not relying on unity gain stability. Maybe you did :-). I'm not actually 100% sure what the above advice means as I'd hope that with a properly run purchasing system one should be able to rely on one's purchasing people to do just that. ie they may not be able to write programs or design hardware but a professionally run purchasing department can perform almost equally impressive miracles in their own specialist area. Needless to say, many fall short of that mark. In another lifetime I worked for a major corporate, where being totally in control of purchasing was a major aim - and one of the companies that I deal with in China also aims at providing consistent component supply in that environment - a good trick indeed if you can do it. In a US environment you'd hope that as long as you bought known-label parts from reputable suppliers that you could rely on data sheets. There are indeed occasional major blowouts in the system (eg bad motherboard caps of some years ago, known fake smps ICs of certain sorts, some Motorola power transistors being widely faked etc), but overall if you can't trust the system to a reasonable extent then data sheets become utterly meaningless. If you start mistrusting data sheets to the stage where you recommend that a major specification not be relied on then you may equally adjudge a given PIC as unlikely to run at full rated clock speed, or to meet sleep current specs or to provide claimed RC oscillator stability over temperature etc. Where would you then draw the line ? Russell -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist