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Feb14-12, 09:39 PM
P: 28
Thanks again,
The input impedance is about 1Gohm/200pf. I need 1nA input, 1 Volt out. Thats a gain of 10^9. So I would need a 100M and a 10. (is that a typo above?)

Just ran some numbers and the lt1052/lt1464 wont cut it. The gain rolls off around 2KHz with a 1pf cap and 100Mohm. 0.5pf just gets 10Khz, but wont the board have more capacitance than that?

I can't seem to find a op-amp that has high enough bandwidth/gain and low input base current.