Abstract: The processing of audio signals is shown in which a first gain-adjustable amplifier is configured to receive a feed forward signal from an input and a second gain-adjustable amplifier is configured to receive a feedback signal from an output. A gain controller supplies a first gain control signal to the first gain-adjustable amplifier, wherein the gain controller supplies a complementary second gain control signal to the second gain-adjustable amplifier, which may be the reciprocal of the first gain control signal. A first combiner is arranged to combine a first output from the first gain-adjustable amplifier with a second output from the second gain-adjustable amplifier. A plurality of filter elements are configured in parallel, wherein each filter element receives an output from the first combiner. A second combiner combines outputs from the filter elements with the original input signal and the filter elements have mutually different filtering characteristic.

Abstract: A bipolar amplification circuit has a control amplifier (101), a dependent current source (102) configured to supply current to an output terminal (104) and driven by an output from the control amplifier (101). A dependent current sink (103) is configured to receive current from the output terminal (104) and is also driven by the output from the control amplifier (101). The control amplifier includes an inverting input (105) and an input signal is supplied to this inverting input. A negative feedback signal of a first polarity is supplied to the inverting input from said dependent current source and a negative feedback signal of a second polarity is supplied to said inverting input from said dependent current sink.