ChrisAtUpw@....... wrote:
> 
....
>     There are two ways of controlling amplifier noise problems. You can fit a
> pair of low noise transistors on the OP-AMP input and get down to less than 1
> nano volt per root Hz. The best you can do this way, with a lot of effort, is
> about 0.3 nano volts per root Hz. You can use a 'chopper stabilised
> amplifier' like the MAX422 or the LTC1050 which, by the way that they work,
> eliminate the 1/f noise. They do add some high frequency noise above about 5
> KHz, but this is easily filtered out. This is good news in general for
> seismolgists, but the price tag is not such good news.
> 
....

Arrow - www.arrow.com - 
has commercial temperature range LTC1050 for $5.55

If you really want to run it above 85 degrees C,
  the LTC1050AMH883   is $24.00

I love 'choppers' - a GREAT improvement over
my original 741's (which were great in the early 1970's  :-)

Cheers
  Ed Thelen

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