Patent ID: 8344795

Claim:
A filter comprising: N unity gain amplifiers, N being at least two, each of said N unity gain amplifiers having a pair of differential input terminals and a pair of differential output terminals, said pair of differential output terminals of a last one of said N unity gain amplifiers comprising filter differential output terminals; a pair of filter differential input terminals; a first pair of variable resistances coupling said pair of filter differential input terminals to said pair of differential input terminals of a first one of said N unity gain amplifiers; N−1 pairs of variable resistances coupling said pairs of differential output terminals of each of said N unity gain amplifiers, other than said last one of said N unity gain amplifiers, to said pairs of differential input terminals of its downstream neighbor; N−1 pairs of variable capacitances coupling said pairs of differential input terminals of each of said N unity gain amplifiers, other than said last one of said N unity gain amplifiers, to said pairs of differential output terminals of its downstream neighbor; and a variable capacitance coupling said pair of differential input terminals of said last one of said N unity gain amplifiers to each other; wherein said N unity gain amplifiers each in turn comprise: a linearized operational transconductance amplifier stage coupled to a corresponding pair of said differential input terminals; and a unity gain buffer with feedback interconnected between said linearized operational transconductance amplifier stage and a corresponding pair of said differential output terminals.