Patent ID: 8907728

Claim:
An amplifier comprising: a first voltage supply configured to supply a first supply voltage; a second voltage supply configured to supply a second supply voltage, the first supply voltage being higher than the second supply voltage; and two parallel signal paths, wherein each signal path is connected to the first and the second voltage supplies and comprises a first amplifier stage and a second amplifier stage, wherein the two signal paths are connected to each other only at a common input node and a common output node, and wherein each signal path is individually connected to the first and second voltage supplies, wherein the first amplifier stages are configured to convert at least a part of an input voltage signal into a signal current, and the signal paths are configured so that the signal current in use drives the respective second amplifier stages to provide an amplified output current to the common output nod, the amplifier further comprising a biasing network configured to bias the amplifier into AB mode, the biasing network comprising, for each signal path, a Zener diode connected between the common input node and the first amplifier stage, so as to in use provide a sum voltage of the input voltage and the Zener voltage of the Zener diode at an input of the first amplifier stage, a capacitor being arranged in parallel with the Zener diode; wherein the first amplifier stage comprises a transistor with an emitter or source and a base or gate, the emitter or source being connected to a voltage supply rail, wherein each signal path further comprises a diode connected between the base or gate of the transistor and the voltage supply rail, wherein a reverse biasing of the transistor causes the diode to conduct.