An amplifier sharing technique in an analog to digital converter (ADC) in
which a cascaded combination of a pre-amplifier and main amplifier is
used to provide the required amplification for a first stage, and only
the main amplifier is used to provide the amplification for the second
stage. Switches and capacitors are used in conjunction such that the
sampling and feedback capacitors of the first stage are connected across
the cascaded combination in a first phase, and sampling and feedback
capacitors of the second stage are connected across the main amplifier in
a second phase. By appropriate choice of parameter values for various
components, the second poles due to the pre-amplifier may be located at
the higher frequency ranges obtaining the required unity gain bandwidth
(UGB) without Miller compensation and/or additional gain.