An amplifier circuit includes first, second, third and fourth
transconductance amplifiers that each have an input, an output and a
transconductance gain. The outputs of the first, second and third
amplifiers communicate with the inputs of the second, third and fourth
amplifiers, respectively. A first resistance has ends that communicate
with the input and the output of the second amplifier, respectively. A
second resistance has ends that communicate with the input and the output
of the fourth amplifier, respectively. Fifth, sixth, seventh and eighth
amplifiers each have an input, an output and a gain. The outputs of the
fifth, sixth and seventh amplifiers communicate with the inputs of the
sixth, seventh and eighth amplifiers, respectively. A third resistance
has one end that communicates with the input of the first amplifier and
an opposite end that communicates with the output of the eighth
amplifier.