OP285,pdf datasheet (Operation

The OP285 is a precision high-speed amplifier featuring the
Butler Amplifier front-end. This new front-end design combines
the accuracy and low noise performance of bipolar
transistors with the speed of JFETs. This yields an amplifier
with high slew rates, low offset and good noise performance
at low supply currents. Bias currents are also low compared
to bipolar designs.
The OP285 offers the slew rate and low power of a JFET
amplifier combined with the precision, low noise and low
drift of a bipolar amplifier. Input offset voltage is laser-trimmed
and guaranteed less than 250 μV. This makes the OP285 useful
in dc-coupled or summing applications without the need for
special selections or the added noise of additional offset
adjustment circuitry. Slew rates of 22 V/μs and a bandwidth
of 9 MHz make the OP285 one of the most accurate medium
speed amplifiers available.