Patent ID: 8390380

Claim:
A circuit comprising: a Darlington transistor pair having an input transistor and an output transistor configured to generate an output signal at an output node in response to an input signal received through an input node; a frequency bias feedback network communicatively coupled between the output transistor and the input node for providing biasing to the Darlington transistor pair as well as for adjusting a phase and amplitude of an amplified version of the input signal that passes through the input transistor and into the frequency bias feedback network, wherein the frequency bias network comprises: a bias transistor coupled between a feedback coupling network and a fixed voltage node; and an electronically controllable phase shifter and amplitude attenuator that is responsive to a control signal and tunable within a ramie that increases a third order intercept point (IP3) to improve an upper frequency band linearity; and the feedback coupling network coupled between the output node and the input node for feeding back to the input node a portion of the amplified version of the input signal that passes through the input transistor.