An amplifying apparatus includes a variable gain amplifying circuit configured to operate in a gain mode selected from a plurality of gain modes in response to a first control signal during operation in an amplification mode, a variable attenuation circuit configured to have an attenuation value that is adjusted in response to a second control signal, and a phase compensation value which compensates for a phase distortion in the selected gain mode, and a control circuit configured to control the selecting of the gain mode, the adjusting of the attenuation value and the phase compensation value, based on the first and second control signals.

The disclosed embodiments include an audio amplifier system configured to provide a total harmonic distortion (THD) controlled clip detector and an automatic gain limiter (AGL) solution for a closed-loop amplifier. The audio amplifier system is capable of maintaining high power output without hard distortion (i.e., hard clipping) for providing better acoustics, while preventing damage to the system.

Provided is a power amplification circuit that includes: a first transistor that has an emitter to which a first radio frequency signal is supplied, a base to which a first DC control current or DC control voltage is supplied and a collector that outputs a first output signal that corresponds to the first radio frequency signal; a first amplifier that amplifies the first output signal and outputs a first amplified signal; and a first control circuit that supplies the first DC control current or DC control voltage to the base of the first transistor in order to control output of the first output signal.

An amplifier for a radio communications system in a shielded tunnel is disclosed. In one example, the amplifier comprises a processor configured to execute a plurality of modules comprising a gain control module and an attenuation control module. Methods and systems are further provided for controlling and monitoring amplifier characteristics.

Techniques and mechanisms for mitigating signal deterioration in communications between two circuit boards. In an embodiment, a packaged device accommodates coupling to a first circuit board which, in turn, accommodates connection to a second circuit board. In one such embodiment, an amplifier circuit of the packaged device includes an amplifier circuit which comprises a variable resistor and an active circuit element coupled thereto. The device receives via one of the circuit boards a control signal and a voltage which configure the amplifier circuit to provide an impedance matching for communication between the circuit boards. In another embodiment, the device comprises multiple common gate amplifiers which are variously configurable each to provide a respective impedance matching for communications between a motherboard and a dual in-line memory module.

A signal amplifier having an input impedance that varies over different bias currents, the signal amplifier comprising a compensation stage including a switchable variable resistance configured to provide a targeted adjustment to the input impedance. A signal amplifier comprising: a variable-gain stage configured to provide a plurality of gain levels that result in different input impedance values; and a compensation stage having a switchable variable resistance configured to provide a targeted adjustment to a respective input impedance. a compensation stage having an output coupled to an input of the gain stage, the compensation stage including a plurality of band selection switches coupled to the plurality of input nodes and a plurality of switchable variable resistance branches coupled to the band selection switches, individual switchable variable resistance branches configured to provide a targeted adjustment to a respective input impedance.

A variable gain amplifier circuit including a first amplifier, a second amplifier, and a variable capacitor connected in series between the first amplifier and the second amplifier is disclosed. As a gain of the variable gain amplifier circuit varies, the input impedance, output impedance, noise figure and third-order output intercept point (OIP3) of the variable gain amplifier circuit remain unchanged.

An output power stabilization circuit includes: a first variable attenuator for attenuating a high-frequency signal inputted thereto; a second variable attenuator for attenuating the high-frequency signal outputted from the first variable attenuator; an output power detection circuit for monitoring the high-frequency signal outputted from the second variable attenuator and outputting an output power detection signal; a temperature monitoring circuit for outputting a temperature monitoring signal; a control circuit for outputting a first control signal for controlling the attenuation amount in the first variable attenuator and a second control signal for controlling the attenuation amount in the second variable attenuator, based on an output power setting signal and the temperature monitoring signal, by referring to previously stored table data; and an attenuation amount setting circuit for making comparison between the first control signal and the output power detection signal and outputting a first attenuation amount adjustment signal for adjusting the attenuation amount in the first variable attenuator.

A variable gain amplifier circuit including a first amplifier, a second amplifier, and a variable capacitor connected in series between the first amplifier and the second amplifier is disclosed. As a gain of the variable gain amplifier circuit varies, the input impedance, output impedance, noise figure and third-order output intercept point (OIP3) of the variable gain amplifier circuit remain unchanged.

An apparatus comprises an amplifier having a predefined linear range and a shunt load. The shunt load may be connected to an output, an input, or between gain stages of the amplifier. An impedance of the shunt load dynamically varies in response to a level of a signal presented at a node formed by interconnection of the shunt load and the amplifier, extending linearity of the amplifier beyond the predefined range.