Driver circuit with output common mode voltage control

An amplifier circuit having a minimized output common mode voltage, the amplifier circuit comprising:

• a differential output amplifier including first and second inputs, and first and second outputs forming first and second outputs, respectively, of the amplifier circuit, the differential output amplifier having a passive element as a bias source for establishing a bias current in the differential output amplifier;
• a common mode amplifier including first and second inputs forming first and second inputs, respectively, of the amplifier circuit, and first and second outputs, the first and second outputs of the common mode amplifier being coupled to the first and second inputs, respectively, of the differential output amplifier;
• and
• a control amplifier including a first input for receiving a reference signal coupled thereto, a second input for receiving a voltage corresponding to an output of the amplifier circuit, and an output operatively connected to the common mode amplifier in a feedback arrangement, the control amplifier generating a control signal for at least partially controlling an output voltage swing of the amplifier circuit in response to a difference between the reference signal and the voltage corresponding to an output of the amplifier circuit;
• wherein the differential output amplifier is responsive to the common mode amplifier for providing a voltage at the outputs of the amplifier circuit that is substantially independent of an input signal presented to the inputs of the amplifier circuit.

In a driver circuit comprising a differential amplifier having a passive element as a bias source for establishing a bias current in the differential amplifier, the differential amplifier including an input stage operatively coupled to a corresponding load device, a method for providing a minimized output common mode voltage in the driver circuit comprising:

• generating a feedback control signal corresponding to a difference between a reference signal coupled to the driver circuit and a voltage corresponding to an output voltage of the driver circuit;
• establishing an output common mode voltage of the driver circuit by controlling at least a portion of a bias current flowing through at least one of the input stage and the corresponding load device of the differential amplifier in response to the feedback control signal, thereby providing an output voltage at the output of the driver circuit that is substantially independent of an input signal presented to an input of the driver circuit;
• generating a second feedback control signal corresponding to a difference between a second reference signal coupled to the driver circuit and a voltage corresponding to the output voltage of the driver circuit;
• and
• controlling an output voltage swing of the driver circuit in response to the second feedback control signal.