Power amplifier output circuit arrangements with mutual coupling between inductors

Abstract

Embodiments of an RF amplifier include a transistor with a control terminal and first and second current carrying terminals, and a shunt circuit coupled between the first current carrying terminal and a ground reference node. The shunt circuit includes a first shunt inductive element, a second shunt inductance, and a shunt capacitor coupled in series. Instead of a separate inductive element, the second shunt inductance may be achieved via magnetic coupling of the first shunt inductive element and an envelope inductive element of a video bandwidth circuit that is coupled between an RF cold point node (between the first and second shunt inductances) and the ground. Alternatively, an envelope inductance in the video bandwidth circuit may be achieved via magnetic coupling of first and second shunt inductive elements. A better RF cold point may be achieved without physically incorporating separate inductive elements, allowing for reduction in cost and size.