Patent ID: 8289077

Claim:
A signal processor comprising an amplifier comprising: a pair of complementary differential pairs such that one differential pair comprises transistors having a polarity opposite to that of transistors in the other differential pair, the one and the other differential pair being coupled to commonly receive a differential input signal, which has a common mode component; and a current combining circuit arranged to combine output currents of the one and the other differential pair so as to obtain an output current that varies as a function of the differential input signal, the one and the other differential pair being each provided with a biasing circuit for providing a tail current that varies with the common mode component in a substantially linear fashion, the current combining circuit comprising: a pair of current-inverting buffers, each current-inverting buffer comprising an input node that is coupled to a first supply voltage line via a biasing circuit for applying a bias current to the input node, one and the other current-inverting buffer being coupled to receive an output current and a complementary output current, respectively, of one differential pair at their respective input nodes; a current mirror for mirroring an output current of one current-inverting buffer, the current mirror comprising an input branch and an output branch, each branch including a transistor having a main terminal that is coupled to a second supply voltage line via an impedance, the input branch and the output branch being coupled to receive an output current and a complementary output current, respectively, of the other differential pair at the respective main terminals of the respective transistors, wherein the gate terminal of the transistor included in the input branch of the current mirror is coupled to the drain terminal of the transistor included in the input branch of the current mirror; and an output node coupled to receive an output current of the other current-inverting buffer and coupled to receive an output current of the current mirror, the amplifier being provided with a feedback circuit so that the differential input signal represents a difference between an input signal and an output signal of the amplifier.