Analog Devices, Inc.
Bias modulation active linearization for broadband amplifiers

Abstract:

A power amplifier circuit for broadband data communication over a path in a communication network can reduce or avoid gain compression, provide low distortion amplification performance, and can accommodate a wider input signal amplitude range. A dynamic variable bias current circuit can be coupled to a differential pair of transistors to provide a dynamic variable bias current thereto as a function of input signal amplitude. Bias current is increased when input signal amplitude exceeds a threshold voltage established by an offset or level-shifting circuit. The frequency response of the bias current circuit can track the full frequency content of the input signal, rather than its envelope. Gain degeneration can be modulated in concert with the bias current modulation to stabilize amplifier gain.