Exemplary embodiments of the present disclosure are related to baseband filters. A device may include a digital-to-analog converter (DAC) configured to output a DC current. The device may also include an operational amplifier coupled to an output of the DAC and configured to bias an input stage of the operational amplifier with the DC current.

Exemplary embodiments of the present disclosure are related to baseband filters. A device may include a digital-to-analog converter (DAC) configured to output a DC current. The device may also include an operational amplifier coupled to an output of the DAC and configured to bias an input stage of the operational amplifier with the DC current.

A feedback gate bias circuit for use in radio frequency amplifiers to more effectively control operation of LDFET, GaNFET, GaAsFET, and JFET type transistors used in such circuits. A transistor gate bias circuit that senses drain current and automatically adjusts or biases the gate voltage to maintain drain current independently of temperature, time, input drive, frequency, as well as from device to device variations. Additional circuits to provide temperature compensation, RF power monitoring and drain current control, RF output power leveler, high power gain block, and optional digital control of various functions. A gate bias circuit including a bias sequencer and negative voltage deriver for operation of N-channel depletion mode devices.

An RF amplifier module that has a plurality of amplifiers wherein at least one of the amplifiers is powered via an envelope tracking module. The biasing input of at least one of the amplifiers is provided to the first amplifier to power the first amplifier to reduce power consumption. The first amplifier may also be powered via fixed biasing to provide greater stability of the module.

Circuitry includes a balanced amplifier and bias adjustment circuitry. The bias adjustment circuitry is coupled to the balanced amplifier and is configured to measure an RF termination voltage across an output termination impedance of the balanced amplifier and adjust a bias voltage supplied to the balanced amplifier based on the RF termination voltage. Notably, the RF termination voltage is proportional to a voltage standing wave ratio (VSWR) of the balanced amplifier, and thus enables an accurate measurement thereof. By using the RF termination voltage to adjust a bias voltage supplied to the balanced amplifier, overvoltage and/or thermally stressing conditions of the balanced amplifier as a result of high VSWR may be avoided while simultaneously avoiding the need for large or expensive isolation circuitry.

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 amplifier circuit includes a carrier amplifier that amplifies a radio frequency signal; a peak amplifier that amplifies the radio frequency signal; and a control circuit including a first variable bandpass characteristic circuit configured such that a bandpass characteristic for passing the radio frequency signal is variable according to a supply voltage and a detector that detects the radio frequency signal passing through the first variable bandpass characteristic circuit. The control circuit controls the bias of the peak amplifier according to a detection result of the detector.

This application relates to methods and apparatus for clipping prevention. A driver apparatus for driving a transducer has a switching driver configured to switch at least one output node between different switching voltages with a controlled duty-cycle to drive an output signal across the transducer. A clipping prevention controller is configured to control a gain applied to the input signal so as to provide limiting of the input signal to avoid clipping of the output signal. The clipping prevention controller is configured to dynamically control at least one limiting threshold used to determine when to apply limiting of the input signal based on an indication of load resistance of the transducer and the input voltage to the switching driver.

A radio-frequency circuit includes an amplifier circuit, a bias circuit, a bias control circuit, a comparing section, a signal input terminal, an antenna terminal, an attenuation circuit, and a control unit. The amplifier circuit includes a specific transistor. The bias circuit supplies a bias current or a bias voltage to the input terminal of the specific transistor. The bias control circuit supplies a control current or a control voltage to the bias circuit. The comparing section compares a threshold voltage with a power supply voltage of a power supply terminal connected to the output terminal of the specific transistor. The attenuation circuit is connected in a signal path between the signal input terminal and the antenna terminal and is capable of attenuating the radio-frequency signal. The control unit changes an attenuation of the attenuation circuit in accordance with a compared result of the comparing section.

A radio frequency module that includes a power amplifier and a load modulator. The power amplifier is configured to directly receive a battery voltage and to receive a radio frequency input signal. The power amplifier is further configured to amplify the radio frequency input signal using the battery voltage to generate a radio frequency output signal. The load modulator is configured to load-modulate the power amplifier. The radio frequency module may be included in a front end module, which may itself be included in a mobile device.