1265results about "Amplifier modifications to reduce detrimental impedence" patented technology

Provided is a power amplifier which fits to a deep-submicron technology in radio frequency wireless communication. The power amplifier includes a cascode including a first transistor which receives and amplifies an input signal, and a second transistor which is connected to the first transistor in series and operated by a DC bias voltage; a third transistor which is connected between the cascode and an output end, operated by a dynamic gate bias and outputting a signal; and a voltage divider which includes first and second capacitors that are connected between the output end, i.e. a drain of the third transistor, and a ground in series, and provides the dynamic bias to a gate of the third transistor.

A method and apparatus to control output power of a digital amplifier capable of automatically determining an impedance of an earphone or headphone connected to a portable audio device and outputting a power that is optimized according to the impedance. The apparatus is usable with a digital amplification device and includes a signal processing unit to convert a pulse signal into a direct current (DC) voltage by power-amplifying the pulse signal, an impedance measuring unit to connect a resistance device between the signal processing unit and a speaker unit and to detect a voltage value applied to the resistance device and the speaker unit, and a micom unit to generate a pulse signal having a predetermined duty cycle in the signal processing unit if the speaker unit is connected to the device, to determine an impedance of the speaker unit based on the voltage value detected by the impedance measuring unit, to control a power amplification by providing a voltage level control signal to the signal processing unit according to the determined impedance, and to control an audio level in an audio reproduction mode accordingly.

According to an exemplary embodiment, a multimode power amplifier configured to receive an RF input signal and provide an RF output signal in linear and saturated operating modes includes an output stage configured to receive a fixed supply voltage and to provide the RF output signal. The multimode power amplifier further includes at least one driver stage coupled to the output stage, where the at least one driver stage is configured to receive the RF input signal and an adjustable supply voltage. The adjustable supply voltage controls an RF output power of the RF output signal when the multimode power amplifier is in the saturated operating mode. The at least one driver and the output stage are each biased by a low impedance voltage in the linear and saturated operating modes. The adjustable supply voltage can be controlled by a fixed control voltage in the linear operating mode.

A cascode circuit with improved withstand voltage is provided. The cascode circuit includes three or more transistors, such as MOSFET transistors. Each transistor has a control terminal, such as a gate, and two conduction terminals, such as a drain and a source. The conduction terminals are coupled in series between two output terminals, such as where the drain of each transistor is coupled to the source of another transistor. A signal input is provided to the gate for the first transistor. Two or more control voltage sources, such as DC bias voltages, are provided to the gate of the remaining transistors. The DC bias voltages are selected so as to maintain the voltage across each transistor to a level below a breakdown voltage level.

A low noise amplifier (LNA) operates over multiple frequency bands while occupying less silicon area than known LNA implementations. The LNA includes output matching that can be tuned by an adjustable inductor together with a tunable capacitor bank.

An amplifier comprises a source degeneration inductance and at least two field effect transistors coupled in parallel and having mutually different gate biasing. Source connections of the field effect transistors are coupled along different positions of the source degeneration inductance.

A fully integrated, programmable mixed-signal radio transceiver comprising a radio frequency integrated circuit (RFIC) which is frequency and protocol agnostic with digital inputs and outputs, the radio transceiver being programmable and configurable for multiple radio frequency bands and standards and being capable of connecting to many networks and service providers. The RFIC includes a tunable resonant circuit that includes a transmission line having an inductance, a plurality of switchable capacitors configured to be switched into and out of the tunable resonant circuit in response to a first control signal, and at least one variable capacitor that can be varied in response to a second control signal, wherein a center resonant frequency of the resonant circuit is electronically tunable responsive to the first and second control signals that control a first capacitance value of the plurality of switchable capacitors and a second capacitance value of the at least one variable capacitor.

A method and system for providing a mixed-mode (current- and voltage-source) audio amplifier is disclosed. The mixed-mode amplifier includes a voltage sensing feedback path including a first network comprising at least one circuit; and a current sensing feedback path including a second network comprising at least one circuit. According to the method and system disclosed herein, the first and second networks vary an output impedance or transconductance of the amplifier as a function of frequency of the input voltage signal, such that at a first frequency range, the amplifier operates substantially as a current amplifier, and at a second frequency range, the amplifier operates substantially as a voltage amplifier, thereby inheriting distortion reduction of the current amplifier and stability of the voltage amplifier.

A mixer includes a reference current source, a programmable gain RF transconductance section or an RF transconductance section, switching quad native transistors or switching quad transistors, and a folded-cascoded common mode output section or an output section. When the mixer included the programmable gain RF transconductance section, the gain of the mixer is adjustable. When the mixer includes the switching quad native transistors, flicker noise of the mixer is reduced. When the mixer includes the folded-cascoded common mode output section, the mixer operates reliably from low supply voltages.

A power amplifier circuit comprising a transistor for receiving a signal to be amplified at an input and for outputting an amplified signal at an output; a modulated power supply connected to the transistor output; and a resistive element connected at the transistor output such that a low impedance is maintained at the transistor output across a range of operational frequencies.

A cascode circuit includes a first field effect transistor which has a source terminal grounded, a second field effect transistor which has a source terminal connected to a drain terminal of the first field effect transistor, and a first capacitor connected between the source terminal of the first field effect transistor and a gate terminal of the second field effect transistor. The first field effect transistor and the second field effect transistor are cascode-connected successively. A capacitance value of the first capacitor is 0.01 to 10 times that between the gate and source terminals of the second field effect transistor.

A variable capacitor is formed by a multilayer circuit board having a plurality of dielectric layers; a first conductive plate, provided within the multilayer circuit board, for serving as one electrode of the variable capacitor; a second conductive plate, provided within the multilayer circuit board, for serving as the other electrode of the variable capacitor; a plurality of third conductive plates provided between the first conductive plate and the second conductive plate; and a plurality of switching means provided for grounding the third conductive plates selectively.

A monolithic integrated circuit (IC), and method of manufacturing same, that includes all RF front end or transceiver elements for a portable communication device, including a power amplifier (PA), a matching, coupling and filtering network, and an antenna switch to couple the conditioned PA signal to an antenna. An output signal sensor senses at least a voltage amplitude of the signal switched by the antenna switch, and signals a PA control circuit to limit PA output power in response to excessive values of sensed output. Preferred fabrication techniques include stacking multiple FETs to form switching devices. An iClass PA architecture is described that dissipatively terminates unwanted harmonics of the PA output signal. A preferred embodiment of the RF transceiver IC includes two distinct PA circuits, two distinct receive signal amplifier circuits, and a four-way antenna switch to selectably couple a single antenna connection to any one of the four circuits.

Devices and methods for amplifying weak electric signals are described. The device of the invention includes an amplifier that is fully integrated in a standard CMOS process and is capable of rejecting large DC offsets while amplifying signals down to the sub-Hz range. This result is achieved by using single-transistor MOS "pseudo-resistor" elements to achieve a very low cutoff frequency in the mHz range or lower. When combined with an electrode array or other sensor array, the fully-integrated amplifier is suitable for recording biological and biopotential signals from the mhz range up to and including about 7 kHz. The amplifier also rejects dc offsets at the input and offers a superior power-noise tradeoff than other amplifiers currently available.