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.