The embodiments described herein provide class F amplifiers and methods of operation. So implemented, the class F amplifiers can be used to provide high efficiency amplification for a variety of applications, including radio frequency (RF) applications. In general, the class F amplifiers are implemented with at least one transistor and an output matching network, where the output matching network includes a plurality of resonant circuits configured to facilitate class F amplifier operation. In addition to facilitating class F amplifier operation, the plurality of resonant circuits can also be implemented with other circuit elements to provide output impedance transformation in a way that facilitates efficient amplifier operation.

Embodiments of RF amplifiers and packaged RF amplifier devices each include a transistor, an impedance matching circuit, and a video bandwidth circuit. The impedance matching circuit is coupled between the transistor and an RF I/O (e.g., an input or output lead). The video bandwidth circuit is coupled between a connection node of the impedance matching circuit and a ground reference node. The video bandwidth circuit includes a plurality of components, which includes an envelope inductor and an envelope capacitor coupled in series between the connection node and the ground reference node. The video bandwidth circuit further includes a first bypass capacitor coupled in parallel across one or more of the plurality of components of the video bandwidth circuit.

A multi-stage Radio Frequency (RF) power amplifier is presented herein. According to one embodiment, the amplifier comprises: a first amplification stage configured to amplify an input signal to provide a first output signal having a phase distortion; a second amplification stage having an input and configured to amplify the first output signal that is received at the input to provide a second output signal, wherein the second output signal has a carrier frequency (F.sub.C) modulated by a signal content (S) having a signal content bandwidth (F.sub.S); and a resonant circuit comprising an inductor and a capacitor and having a resonant frequency (F.sub.R), the resonant circuit coupled to the input of the second amplification stage and compensating for the phase distortion caused by the first amplification stage at frequencies within the signal content bandwidth F.sub.S, wherein the resonant frequency F.sub.R is less than the signal content bandwidth F.sub.S.

Example embodiments relate to compact Doherty amplifiers having improved video bandwidth. One example embodiment includes an amplifier. The amplifier includes a package having a substrate. The amplifier also includes at least one amplifier unit arranged in the package. Each amplifier unit includes an input terminal and an output terminal. Each amplifier unit also includes an active semiconductor die on which a high-power transistor is integrated. Additionally, each amplifier unit includes an input matching capacitor and an output matching capacitor. Further, each amplifier unit includes a third inductor connecting an output of the high-power transistor to the output matching capacitor. In addition, each amplifier unit includes a fourth inductor connecting an input of the high-power transistor to the input matching capacitor. Yet further, each amplifier unit includes an output resonance network including a series connection of a first inductor and a first capacitor. Each amplifier unit includes a passive semiconductor die.

An amplifier circuit includes a divider that divides an input signal into a first signal and a second signal, a first amplifier that amplifies the first signal and output a third signal to a first node, a second amplifier that amplifies the second signal and outputs a fourth signal to a second node, a combiner that combines the third signal and the fourth signal and outputs a combined signal to an output terminal as an output signal, and a processing circuit that includes an input node to which the first and the second nodes are electrically coupled, and allows a signal having a frequency lower than an operating band of the first amplifier and the second amplifier to pass through a reference potential, wherein a coupling degree between the first node and the input node is larger than a coupling degree between the second node and the input node.

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 inductance, a second shunt inductance, and a shunt capacitor coupled in series. The second shunt inductance and the shunt capacitor form a series resonant circuit in proximity to a center operating frequency of the amplifier, and an RF cold point node is present between the first and second shunt inductances. The RF amplifier also includes a video bandwidth circuit coupled between the RF cold point node and the ground reference node.