Output common mode voltage stabilizer over large common mode input range in a high speed differential amplifier

A circuit, comprising:

• a differential input stage including a first input transistor configured to receive a first input signal, a second input transistor configured to receive a second input signal and a first tail current source coupled to supply a first current to the first and second input transistors at a first common connection node, said differential input stage having a pair of outputs;
• wherein the first and second input signals are differential signals having an input common mode voltage;
• a pair of cascode transistors having first conduction terminals respectively coupled to the pair of outputs of the differential input stage and having second conduction terminals configured to respectively generate first and second output signals;
• wherein the first and second output signals are differential signals having an output common mode voltage;
• a sensing circuit coupled to receive the first and second input signals, sense the common mode input voltage and generate a second current modulated as a function of the sensed common mode input voltage;
• and
• a bias generator circuit configured to generate a bias voltage as a function of the second current and apply said bias voltage to control terminals of the pair of cascode transistors.

A method, comprising:

• sensing common mode input voltage of a differential input signal;
• generating a first current modulated as a function of the sensed common mode input voltage;
• amplifying the differential input signal in a differential amplifier having a folded cascode architecture including a pair of cascode transistors to generate a differential output signal having a common mode output voltage;
• generating a bias voltage for application to the pair of cascode transistors in the folded cascode architecture;
• and
• modulating the bias voltage as a function of the first current.