Common-mode control structures and signal converter systems for use therewith

An amplifier that provides an output signal in response to an input signal and a common-mode reference signal, comprising:

• a transistor that has a control terminal and provides a tail current whose amplitude corresponds to signals at said control terminal;
• a differential pair of transistors that respectively have first and second current terminals and are coupled to steer said tail current between said first and second current terminals in response to said input signal to thereby provide said output signal;
• a first signal divider coupled across said first and second current terminals to provide a first sense signal;
• a second signal divider coupled across said first and second current terminals to provide a second sense signal to said control terminal;
• and
• a differential amplifier that provides a feedback signal to said control terminal in response to the difference between said first sense signal and said common-mode reference signal.

A signal converter system for converting analog input signals into corresponding digital codes, the system comprising:

• a sampler that provides output signals which are samples of said input signal;
• N converter stages that successively process said samples to corresponding digital bits wherein all but a last one of said stages passes output signals in the form of residues to a succeeding stage for processing;
• and
• an aligner/corrector that provides said corresponding digital code in response to said digital bits;
• wherein at least one of said sampler and said stages generates its respective output signals with an amplifier that includes:
• a transistor that has a control terminal and provides a tail current whose amplitude corresponds to signals at said control terminal;
• a differential pair of transistors that respectively have first and second current terminals and are coupled to steer said tail current between said first and second current terminals to thereby provide said respective output signals;
• a first feedback path coupled from said first and second current terminals to said control terminal and configured to provide a feedback signal that responds to a common-mode reference signal and that has a first feedback gain and a first feedback bandwidth;
• and
• a second feedback path coupled from said first and second current terminals to said control terminal and configured to provide a second feedback gain that is less than said first feedback gain and a second feedback bandwidth that is greater than said first feedback bandwidth.