Switching amplifiers

A controller for controlling a switching amplifier to modulate voltages at first and second output nodes so as to drive a load connected between said first and second output nodes with a differential drive signal based on an input signal, wherein:

• the controller is configured to control the switching amplifier to selectively operate in at least a first mode or a second mode, wherein in each of the first and second modes, the first and second output nodes are modulated between switching voltages with a controlled duty-cycle and at least one of the switching voltages is different in the first mode compared to the second mode;
• the controller is configured to control the mode of operation based on the input signal such that the switching amplifier can dynamically swap between the first and second modes;
• the controller is configured such that, in steady-state operation in the first mode a common-mode voltage applied to the first and second output nodes has a first value and in steady-state operation in the second mode a common-mode voltage applied to the first and second output nodes has a second value, different to the first value;
• wherein at least one of first values and the second values is not equal to a voltage which is halfway between the switching voltages used in that mode.