Device and method for bias control of class A power RF amplifier

摘要

A circuit and technique are provided to control bias setting to an FET based common source RF amplifier that can operate with large signals present. The circuit and technique described herein use a second FET in an identical circuit having the gate circuits connected in parallel and being sourced by the same drain voltage that serves as a reference to a first circuit bias setting. The drain current in a first FET will include both the bias and RF amplification current, whereas the second FET only carries the bias current. Because the devices and circuits are matched, the gate voltage variations will appear in both FETs thereby providing regulation of the drain current.

主权项

1. An RF amplifier comprising:
a first transistor having a gate coupled to an input matching circuit and a first input tee and a first transistor drain coupled to an output matching circuit and a first output tee; a second transistor having a gate coupled to a second input tee and a second transistor drain coupled to a second output tee; a single drain voltage bias supply in electrical communication with both the first transistor drain and the second transistor drain; and a control circuit coupled between the first and second input tees and the first and second output tees, the control circuit being configured to control a drain current of the first transistor, the control circuit comprising: (1) a current sensor coupled between the first output tee and the second output tee, and (2) an operational amplifier having an inverting input coupled to an output of the current sensor and a non-inverting input coupled to a scalable pulse voltage source.