offset adjusting

[danial stocks]

>:::-the usuall offset voltage problems, though you can buy arround 100uV
>::: today from the shelf. Typical max input voltage should be 1V,
>::: so that's 100uV/1V ->0.01% error. Not that bad.
>
>Yes , with V1, V2 = 1V. But at the lower side there will be 1mV,
>so 10% untrimmed error!  Ok with V1max ~ 5V, 1:1000 range
>and trimming we might get to 30uV/5mV ~ 0.6% error, that's
>still a lot,and then a lot of triming is required for the
>reference voltages as well...
>
>This could get very tough for low control voltages...
>
>
well folks, the free trade zone database finally identified some nice weird 
chips for me from my weird chips box.. the LMC669 is apparently 
discontinued, but there must be something out there like it.. it's an auto 
op amp offset calibrator.. attach to the summing node and the + in and it 
claims to auto calibrate the offset to [typ] 5uv! independent of supply 
vtg,time,temp, and req's no user offset adj. this could be the solution to 
many a finicky vco prob! unfortunately Ive only got 1...
cheers,
dan
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