Samuel Groner
Well-known member
I quickly measured differential and common-mode current noise density of an AD797 and LT1115. The AD797 gave 1.4 pA/sqrt(Hz) and 2.1 pA/sqrt(Hz) while the LT1115 showed 1 pA/sqrt(Hz) and 2.3 pA/sqrt(Hz). Hence it is clear that both opamps (and not just the LT1115) show drastic amounts of common-mode current noise. Which one is quieter depends on the application; for the LT1115 the funny situation occurs that with a 100k resistor in series with *both* inputs total noise is actually lower than with just one resistor in series with one input.
Samuel
Samuel