I am undertaking a project in which we have to measure very low level (1pA and above) current.
We did go through the ADA4530-1R-EBZ-TIA evaluation board user guide
and also the reference design - EVAL-CN0407-SDPZ.
The ADA4530-1R-EBZ-TIA evaluation board has a 10Gohm SMT feedback resistor.
The user guide also says about the THROUGH HOLE RESISTOR configuration.
The Circuit Note of EVAL-CN0407-SDPZ says that it has the through hole 10Gohm Glass resistor
on the Low Leakage Mezzanine board (EVAL-CN0407-1-SDPZ).
Since the glass resistor is a hermetically sealed resistor and an absolute requirement for low leakage,
we need the glass resistor in our configuration.
But we don't need the ADC provided with the CN0407 evaluation board.
The dilemma is : We just need the Low Leakage Mezzanine board (with glass resistor)
of the CN0407 evaluation board.
We need the ADA4530-1R-EBZ-TIA evaluation board with glass resistor.
Even though the board is configurable according to our needs, i.e. we can solder the glass resistor,
we do not want to take any risk since it may degrade our low current measurement.