Differential amplifiers with enhanced gain and dynamic range

An amplifier that processes signals from an amplifier input port to an amplifier output port, comprising:

• a first differential pair of transistors that define said amplifier input port and a first differential port and are coupled to steer a first tail current across said first differential port in response to signals at said amplifier input port:
• a second differential pair of transistors that define a second differential port for receiving signals from said first differential port and that define said amplifier output port and are coupled to steer a second tail current across said amplifier output port in response to signals at said second differential port;
• and
• at least one feedback circuit arranged to mirror and adjust at least one of said first and second tail currents in response to signals from at least one of said second differential port and said amplifier output port;
• wherein said feedback circuit includes:
• a current source;
• a reference generator that provides a reference signal;
• a feedback amplifier configured to mirror said second tail current from said current source to said second differential pair and provide an error signal to adjust said second tail current in response to a difference between said reference signal and a common-mode signal at said amplifier output port.

An amplifier that processes signals from an amplifier input port to an amplifier output port, comprising:

• a first current source
• a first differential pair of transistors that define said amplifier input port and a first differential port and are coupled to steer a first tail current across said first differential port in response to signals at said amplifier input port;
• first current-source transistors biased to provide currents;
• two sets of cascode transistors inserted to couple said first current-source transistors to said first differential port;
• a second current source
• a second differential pair of transistors that define a second differential port for receiving signals from said first differential port and that define said amplifier output port and are coupled to steer a second tail current across said amplifier output port in response to signals at said second differential port;
• second current-source transistors biased to provide currents;
• a set of cascode transistors inserted to couple said second current-source transistors to said amplifier output port;
• a first feedback circuit arranged to mirror said first tail current from said first current source and adjust said first tail current in response to signals from said second differential port;
• and
• a second feedback circuit arranged to mirror said second tail current from said second current source and to adjust said second tail current in response to signals from said second differential port.

A signal converter system for converting an analog input signal into a corresponding digital code, the system comprising:

• at least two converter stages coupled in series to receive said analog input signal and each convert a respective portion of said analog input signal into a respective code portion of said digital code wherein at least one of said stages includes:
• an analog-to-digital converter that provides that stage's code portion and a selected one of a set of reference signals;
• and
• a switched-capacitor network that generates the respective portion of a succeeding one of said converter stages with the aid of a differential amplifier that processes signals from an amplifier input port to an amplifier output port and includes:
• a) a first current source;
• b) a first differential pair of transistors that define said amplifier input port and a first differential port and are coupled to steer a first tail current across said first differential port in response to signals at said amplifier input port;
• c) a second current source;
• d) a second differential pair of transistors that define a second differential port for receiving signals from said first differential port and that define said amplifier output port and are coupled to steer a second tail current across said amplifier output port in response to signals at said second differential port;
• and
• e) a first feedback circuit arranged to mirror said first tail current from said first current source and adjust said first tail current in response to signals from said second differential port;
• and
• f) a second feedback circuit arranged to mirror said second tail current from said second current source and to adjust said second tail current in response to signals from said second differential port.