Patent ID: 7728658

Claim:
An amplifier providing an output containing low noise and low distortion up to a maximum operating frequency, the amplifier comprising: a digital modulator that produces an output at a first sampling frequency; power devices that produce an output; an analog-to-digital converter (ADC) that receives an input in dependence on the output of the power devices; and a low-delay filter fed in dependence on the output of the ADC; wherein an input to the digital modulator is derived in dependence on an output of the low-delay filter, and wherein the ADC operates at a second sampling frequency that is higher than the first sampling frequency, and wherein the low-delay filter has an impulse response that is asymmetric, and wherein the low-delay filter provides attenuation in critical frequency ranges, each critical frequency range being centered on a harmonic of the first sampling frequency and being of a width equal to twice the maximum operating frequency.