Re MAXIM filters:

I have a whole drawer full of MAXIM samples (They managed to mis-spell
my name so every variation gets the product literature with the FREE
sample postcards).

We evaluated a number of IC filters, and found that for our needs in
preamps for seismic telemetry stations, they:
1. Are noisy, by our need for greater than 90db SNR.
2. Are power hungry (we worry about 10 microamps per amplifier)
3. Don't really save over parts since an output buffer is needed.
4. The single-side supply requires AC input/output coupling
of the bipolar ground-referenced seismic and VCO signals, which
complicates any design for a very low frequency or DC response.
A VCO (voltage controlled oscillator) is used for telemetry.
5. We actually have lots of single amps to use in the 2-amp 4-pole
analog filter since we screen all of them for noise, using the quietest 
in the first stage, since its noise is amplified by the second. We use
a unity gain filter configuration to reduce the contribution of 1/f
noise and resistor thermal noise.

Regards,
Sean-Thomas
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