An apparatus includes an input amplifier stage and a switch that has a first terminal at a virtual ground input of the input amplifier stage.

Embodiments disclosed herein relate to impedance matching for outputting wide-band signals in radio frequency applications. In an example, a circuit including a low-noise amplifier (LNA) sub-circuit and a tuning sub-circuit is provided. The LNA sub-circuit is configured to couple to an antenna and includes a transistor that includes a gate, a source, and a drain, a first inductor that includes a first terminal configured to couple to the antenna and includes a second terminal, a second inductor that includes a first terminal coupled to the first terminal of the first inductor and includes a second terminal coupled to the gate of the transistor, and a third inductor that includes a first terminal coupled to the source of the transistor and includes a second terminal. The tuning sub-circuit is coupled to the source of the transistor.

Apparatus and methods for envelope tracking are disclosed. In one embodiment, a power amplifier system including a power amplifier and an envelope tracker is provided. The power amplifier is configured to amplify a radio frequency (RF) signal, and the envelope tracker is configured to control a supply voltage of the power amplifier using an envelope of the RF signal. The envelope tracker includes a buck converter for generating a buck voltage from a battery voltage and a digital-to-analog conversion (DAC) module for adjusting the buck voltage based on the envelope of the RF signal to generate the supply voltage for the power amplifier.

A direct current (DC)-DC converter, which includes a charge pump buck power supply and a buck power supply is disclosed. The charge pump buck power supply includes a charge pump buck converter, a first inductive element, and an energy storage element. The charge pump buck converter and the first inductive element are coupled in series between a DC power supply, such as a battery, and the energy storage element. The buck power supply includes a buck converter, a second inductive element, and the energy storage element. The buck converter and the second inductive element are coupled in series between the DC power supply and the energy storage element. As such, the charge pump buck power supply and the buck power supply share the energy storage element.

Apparatus and methods for envelope tracking systems are provided. In certain configurations, an envelope tracking system includes a digital filter that generates a filtered envelope signal based on a digital envelope signal representing an envelope of a radio frequency signal, a buck converter controllable by the filtered envelope signal and including an output electrically connected to a power amplifier supply voltage, a digital-to-analog converter module including an output electrically connected to the output of the buck converter and that provides an output current, and a digital shaping and delay circuit configured to generate a shaped envelope signal based on shaping the filtered envelope signal. The shaped envelope signal controls a magnitude of the output current, and the digital shaping and delay circuit controls a delay of the shaped envelope signal to align the output of the digital-to-analog converter module and the output of the buck converter.

An apparatus includes an input amplifier stage and a switch that has a first terminal at a virtual ground input of the input amplifier stage.

A radio frequency (RF) switch semiconductor die and an RF supporting structure are disclosed. The RF switch semiconductor die is attached to the RF supporting structure. The RF switch semiconductor die has a first edge and a second edge, which may be opposite from the first edge. The RF supporting structure has a group of alpha supporting structure connection nodes, which is adjacent to the first edge; a group of beta supporting structure connection nodes, which is adjacent to the second edge; and an alpha AC grounding supporting structure connection node, which is adjacent to the second edge. When the group of alpha supporting structure connection nodes and the alpha AC grounding supporting structure connection node are active, the group of beta supporting structure connection nodes are inactive.

Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

A Doherty power amplifier includes a first amplifier with a first output capacitance, a second amplifier with a second output capacitance, a reconfigurable impedance inverter, and a variable output impedance transformer. The reconfigurable impedance inverter includes a combining node and first, second, and third variable networks. The first variable network and the first amplifier output capacitance establish a first amplifier effective output capacitance that is less than the first output capacitance. The second variable network provides a series inductance between the first amplifier output and the combining node. The third variable network and the second amplifier output capacitance establish a second amplifier effective output capacitance that is less than the second output capacitance. The output impedance transformer includes a fourth variable network that establishes a combining node impedance. The first, second, and third variable networks and the output impedance transformer may be reconfigured based on traffic loading conditions.