A buffer for the input to an A/D converter operates in two stages. During
the first stage, the input is not provided directly to the A/D converter;
rather, a buffered output which corresponds to the input is provided to
the A/D converter so as to pre-charge the sampling capacitor of the A/D
converter to a value that is substantially close to the input. In the
second stage, the input is provided directly to the A/D converter, which
charges its sampling capacitor to the value of the input. Because the
sampling capacitor is pre-charged to a value that is substantially close
to the input, and because the sampling capacitor is charged to this value
through a buffer, reflections back into the input which otherwise might
have been caused by a difference between the value stored on the sampling
capacitor and the input are largely avoided.