What advantages does the ADA4350 have over other traditional switchable gain
TIAs or the fixed gain TIA+PGA approach?
Compared to the traditional switchable gain TIAs, the ADA4350 employs the
Kelvin switching technique which eliminates non-linear errors in the
system due to the switch resistances. See question 2 and the Theory of
Operation Section on the datasheet for more details.
Compared to the fixed gain TIA+PGA approach, the ADA4350 implements the
gain stage in the TIA amplifier using external resistors to reduce the
overall noise contribution. This means when you use a x10 resistor to
implement a x10 gain, the noise gain follows the Johnson noise equation
which is only times.