A chopper amplifier and method of operation are described. The chopper amplifier comprises a first chopper arranged to modulate an input signal using a first chopper signal having a chopper frequency. An amplification stage has an input arranged to receive the chopped signal and an output, and supplies an amplified signal at the output. An output chopper is arranged to integrate the amplified signal using a second chopper signal having the chopper frequency to generate an amplified output signal. The amplification stage is further configured to filter the chopped signal to attenuate signal components having frequencies lower than the chopper frequency.

A tower mounted amplifier and a filter. The filter includes a transmission part having a first tunable portion and a reception part having a second tunable portion and a third tunable portion. The transmission part is coupled between a first port and a second port. The second tunable portion of the reception part is coupled between the first port and a third port, and the third tunable portion of the reception part is coupled between a fourth port and the second port. The first tunable portion is configured to work in a first frequency range different from a first pass band in which the second and third tunable portions are controlled to work when a radio frequency signal is to be transmitted from the first port to the second port, the radio frequency signal being rejected by the first tunable portion to the second port.

Technologies are described to DC-couple an integrated amplifier system to a source that provides a signal with an unknown DC component, for example to DC-couple an integrated audio codec to an analog microphone. In one aspect, methods include receiving, by an amplifier, a signal having an unknown DC component, and issuing an amplified signal; low pass filtering, with respect to a cutoff frequency, by a feedback circuit coupled between an output of the amplifier and an input of the amplifier, the amplified signal issued at the output of the amplifier to generate a filtered signal having frequencies lower than the cutoff frequency; and injecting, by the feedback circuit, the filtered signal into the input of the amplifier to cancel the unknown DC component below the cutoff frequency.

A tunable matching circuit for use with ultra-low power RF receivers is described to support a variety of RF communication bands. A switched-capacitor array and a switched-resistor array are used to adjust the input impedance presented by the operating characteristics of transistors in an ultra-low-power mode. An RF sensor may be used to monitor performance of the tunable matching circuit and thereby determine optimal setting of the digital control word that drives the switched-capacitor array and switched-resistor array. An effective match over a significant bandwidth is achievable. The optimal matching configuration may be updated at any time to adjust to changing operating conditions. Memory may be used to store the optimal matching configurations of the switched capacitor array and switched resistor array.

Aspects of this disclosure relate to detecting power associated with an individual carrier of a carrier aggregated signal. In an embodiment, an aggregated carrier including at least a first carrier and a second carrier is provided. An indication of power of the first carrier of the aggregated carrier is detected. Separately from detecting the indication of power of the first carrier, an indication of power of the second carrier of the aggregated carrier is detected. The power associated with a radio frequency (RF) signal provided to an RF source associated with the first carrier can be adjusted based on the indication of power of the first carrier.

A switching amplifier realizes bidirectional energy flow and combines switching and power amplification into one single stage so as to increase system efficiency. The modulator circuit of the amplifier receives and modulates an input signal, and generates and outputs modulated driver signals, which are used by the power driver circuit to generate signals to drive switching transformers of an amplifier circuit of the amplifier, and control signals, which are used to control an output generator circuit so as to allow individual inductors across the load by enabling current flowing through the load to have a path to ground. The amplifier circuit comprises switching transformers as well as circuitries configured to capture energy returned from the load and enable the captured energy to flow back to a power supply circuit of the amplifier through an energy flow-back circuit of the amplifier.

A high frequency power amplifier includes a first high frequency amplifier, a final high frequency amplifier, and a tunable filter. The tunable filter is connected between the first high frequency amplifier and the final high frequency amplifier. The first high frequency amplifier and the final high frequency amplifier are each a multimode/multiband power amplifier. The tunable filter is regulated such that its pass band includes the frequency band of a transmission signal and its attenuation band includes the frequency band of a reception signal in a communication band used in transmission and reception. The pass band and the attenuation band are switched by the tunable filter in accordance with the communication band used in transmission and reception.

An electronic circuit includes an isolation amplifier, having a first input terminal receiving an AC-signal and including a linear opto-isolator. The opto-isolator has a first output terminal that provides a unipolar signal having an AC-component proportional to the input signal. The circuit includes a transimpedance receiver with first and second operational amplifiers. The first amplifier has a second output terminal and first and second differential input terminals, with the first differential input terminal receiving and amplifying the unipolar output signal from the first output terminal providing an output signal from the circuit at the second output terminal. The second amplifier is configured as an integrator, having a third output terminal coupled to the second differential input terminal and having third and fourth differential input terminals, with the third differential input terminal receiving the output signal from the second output terminal and the fourth differential input terminal connected to ground.

An amplifier circuit includes an amplifier configured to receive a radio frequency (RF) input signal from an input node, a bias circuit comprising a reference transistor coupled between a reference current source and ground, and a bias transistor coupled to the reference transistor and configured to generate a main bias current to bias the amplifier, an input power sense circuit coupled to the input node, and an additional transistor coupled to the input power sense circuit and to the bias transistor, the additional transistor configured to generate an additional bias current to bias the amplifier, the additional bias current responsive to a power level of the RF input signal.

A high-frequency signal amplifier circuit is used in a front-end circuit configured to propagate a high-frequency transmission signal and a high-frequency reception signal, and includes an amplifier transistor configured to amplify the high-frequency transmission signal; a bias circuit configured to supply a bias to a signal input end of the amplifier transistor; and a ferrite bead, one end of which is connected to a bias output end of the bias circuit and the other end of which is connected to the signal input end of the amplifier transistor, having characteristics in which impedance in a difference frequency band between the high-frequency transmission signal and the high-frequency reception signal is higher than impedance in DC.