Ultra-low distortion, wide-bandwidth amplifier architecture using actively phase-matched feed-forward linearization

Abstract

An amplifier architecture using actively phase-matched feed-forward linearization includes: a first signal path having a scaling amplifier 40 in series with a main amplifier 42; a second signal path having a replica amplifier 44 in series with a correction amplifier 46; and a combining node 48 that combines the first signal path and the second signal path. This topology places the scaling amplifier 40 in the main signal path. By inverting the scaling factor from β to 1/β, this topology retains the distortion cancellation property while balancing the two signal paths. In this case the scaling amplifier 40 attenuates the input signal rather than amplifying it. The end result remains the same. The main amplifier output signal is lower than the replica amplifier's by a factor of β. This results in a third-order distortion component that is β3 times bigger at the replica amplifier output. By correcting this level down to that at the main amplifier 42, the fundamental component in the feed-forward path is significantly attenuated. When the two signal paths combine, the third-order distortion components cancel while the fundamental is attenuated to a far lesser degree.

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