Wide bandwidth class C amplifier with common-mode feedback

An apparatus comprising:

• an input circuit having a first pair of differential output terminals and that provides a common-mode current;
• and
• an output circuit having:
• a second pair of output terminals;
• a common-gate amplifier that is coupled to the first pair of differential output terminals and second pairs of output terminals and that includes a resistor network;
• a feedback amplifier that is coupled to the resistor network so as to generate a control voltage from a sensed common-mode and a reference voltage;
• a first common-mode feedback circuit that is coupled the feedback amplifier so as to receive the control voltage and that is coupled to provide a first feedback current to the resistor network when the common-mode current is less than a predetermined threshold;
• and
• a second common-mode feedback circuit that is coupled to the feedback amplifier so as to receive the control voltage and that is coupled to provide a second current to the first pair of differential output terminals when the common-mode current is greater than a predetermined threshold.

A method comprising:

• applying a common-mode current to a common-gate amplifier;
• sensing the common-mode current;
• generating a control voltage in response to the sensed common-mode current;
• applying a first feedback current to differential ground of the common-gate amplifier if the common-mode current is less than a predetermined threshold, wherein the first feedback is generated in response to the control voltage;
• and
• applying a second feedback current to input terminals of the common-gate amplifier if the common-mode current is greater than the predetermined threshold, wherein the second feedback is generated in response to the control voltage.