From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-01-28 22:57:49
--- In buildcheapeeg_at_yahoogroups.com, Jim Peters <jim_at_uazu.net> wrote:
> I can get the AD627. Looking at the spec sheet, I'm hopeful, and
> there is a similar circuit in the AD627 spec-sheet showing
> capacitors and resistors on the inputs there.
Hi Jim,
If you switch to AD627, you must recalculate the gain resistor: R6 =
200000 / (G - 5). Other than that, you don't have to change anything.
> I'm thinking of leaving off the drift-correction thing as Andreas
> suggested to start with (they don't have the OP-90) -- I can add it
> later -- but I'll use the capacitors/resistors.
OP-90 is just one of many many types you can choose from. Tom Collura
probably picked it because it has very low current consumption. Try a
OPA277 or TL071. They use more current, but I guess that's not that
important right now.
> I can only get 10% polypropylene capacitors, not 2% ones as
> specified. I can get 5% polystyrene ones, though. Maybe I'll buy
> them all and try them, or get a better multimeter and try and find
> a matching pair.
Don't worry, 5% polystyrene should work ok without matching.
> The spec says the AD627 can drive up to 20mA by itself. Hopefully
> this will be enough for sound-card input.
At these frequencies, that is more than enough. (Of the top of my
head...)
A completely different option is of course to build Jim Meissners
input stage, also tried and tested.
/Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:37 BST