Fully differential class a/ab amplifier and method thereof

A differential amplifier, comprising:

• a first amplifier stage, configured to generate first stage differential output signals based on input differential signals;
• a bias circuit, coupled to the first amplifier stage and a ground, comprising a bias current source and first and second control transistors coupled to the ground through the bias current source, configured to provide a bias current with a desired quiescent current level by the bias current source, and bias the first and second control transistors with the bias current to generate first and second currents, respectively, wherein the first and second control transistors form a differential pair which receives the first stage differential input signals;
• and
• a second amplifier stage, coupled to the bias circuit, comprising first and second output amplifier stages outputting second stage differential output signals, wherein each of the first and second output amplifier stages comprises complementary push and pull transistors coupled in series to each other, and a mirror transistor coupled to the push transistors, the mirror transistor mirrors one of the first and second currents to the push device, and the mirrored current serves to bias the pull transistor.