Patent ID: 8860510

Claim:
A Class AB push pull amplification stage arranged to receive a voltage signal to be amplified and a DC bias voltage, the amplification stage comprising: a combiner to generate a sum input signal by combining the voltage signal with the DC bias voltage; a subtractor to generate a difference input signal by subtracting the voltage signal from the DC bias voltage; a first transistor connected to receive the sum input signal and generate a first part of an amplifier output signal; a second transistor connected to receive the difference input signal and generate a second part of an amplifier output signal; a combiner for combining the first and second parts of the amplifier output signal; a sensing circuit arranged to sense a current flowing in each of the first and second transistors; a control circuit arranged to determine the quiescent current of the first and second transistors in dependence on the sensed currents; and an adjustment circuit arranged to adjust the DC bias voltage in order to minimise variation in the quiescent current.