Datasheet

Data Sheet ADA4001-2
Rev. C | Page 11 of 12
INPUT BIAS CURRENT
Because the ADA4001-2 has a JFET input stage, the input bias
current, due to the reverse-biased junction, has a leakage
current that approximately doubles every 10°C. The power
dissipation of the part, combined with the thermal resistance of
the package, results in the junction temperature increasing 30°C
above ambient. This parameter is tested with high speed ATE
equipment, which does not result in the die temperature
reaching equilibrium. This is correlated with bench
measurements to match the guaranteed maximum at room
temperature in Table 1.
The input current can be reduced by keeping the temperature as
low as possible and using a light load on the output.
NOISE CONSIDERATIONS
The JFET input stage offers very low input voltage noise and
input current noise. The thermal noise of a 1 kΩ resistor at
room temperature is 4 nV/√Hz, thus low values of resistance
should be used for dc-coupled inverting and noninverting
amplifier configurations. In the case of transimpedance
amplifiers (TIAs), current noise is more important.
The ADA4001-2 is an excellent choice for both of these
applications. Analog Devices, Inc., offers a wide variety of low
voltage noise and low current noise op amps in a variety of
processes optimized for different supply voltage ranges. Refer
to the AN-940 Application Note for a complete discussion of
noise, calculations, and selection tables for more than three
dozen low noise, op amp families.