ICL7650S pdf datasheet (2MHz,

The ICL7650S Super Chopper-Stabilized Amplifier offers
exceptionally low input offset voltage and is extremely stable
with respect to time and temperature. It is a direct
replacement for the industry-standard ICL7650 offering
improved input offset voltage, lower input offset voltage
temperature coefficient, reduced input bias current, and
wider common mode voltage range. All improvements are
highlighted in bold italics in the Electrical Characteristics
section. Critical parameters are guaranteed over the
entire commercial temperature range.
Intersil’s unique CMOS chopper-stabilized amplifier circuitry
is user-transparent, virtually eliminating the traditional
chopper amplifier problems of intermodulation effects,
chopping spikes, and overrange lockup.
The chopper amplifier achieves its low offset by comparing
the inverting and non-inverting input voltages in a nulling
amplifier, nulled by alternate clock phases. Two external
capacitors are required to store the correcting potentials on
the two amplifier nulling inputs; these are the only external
components necessary.
The clock oscillator and all the other control circuitry is
entirely self-contained. However the 14 lead version includes
a provision for the use of an external clock, if required for a
particular application. In addition, the ICL7650S is internally
compensated for unity-gain operation.