Op amp enquiry

[ozzy]

Hi all,


Does any one know of some good FET based op amps (100 Meg source
impedance) for battery (9v split supply) operation. In particular:

* 10 microAmp Max supply current
* Low bias current - < 1 pA as well as low drift with temp
* Good PSRR - 90-100 dB as I have to take into consideration battery
loss
* CMRR - 80-90 dB - not excessive as common mode voltages will not
fluctuate a great deal e.g
0-0.1V
* Does not have to be RRIO
* Tailored for Dual supply operation
* Offset voltage (specifically due to offset current) not important -
5-6mV O.K
* Cheap!
* DIP package as it's easy to handle
* Low noise voltage - 10-15 nV/Hz-(suare root) at 1KHz


I was hoping that someone with some experience with Very high source
impedance (100 MEG) probes could help out here. I have had a look at
sites but either they're expensive (e.g Linear tech's over-the-top op
amps) or dont meet the criteria.

Maybe a Bipolar based Opamp with source follower would be simpler? By
the way a dual is needed - part of an Instrumentation Amp.


Regards,


Ozzy.