Systems and methods are provided for reducing the effects of an impedance mismatch between a communications system and a shared communications medium. A communication system, such as a transceiver within a cable modem, switches between various operating modes including a transmit mode, a receive mode, and a standby mode. The standby mode may be used while the transceiver is in an idle state between modes, such as while changing an amplifier gain states in between transmissions. While transitioning between modes, the impedance presented by the communications system can temporarily fluctuate causing unwanted signal reflections to propagate out of the communications system and on to the shared medium. Circuitry within the communications system, such as transmission circuitry including an adjustable attenuator, may be placed into a hybrid attenuation-isolation mode during the transition causing the magnitude of any unwanted signal reflections to be attenuated and reducing the impact on the shared medium.

The present application provides a multimode transmit power control loop, an electronic device, and a method of adjusting a detected operating level of amplified power output from a power amplifier. The multimode transmit power control loop including a feedback path wherein a feedback path signal is coupled to a feedback detection input of the power amplifier via the feedback path. The feedback path includes a mode selection switch having a control input for selectively applying a different impedance circuit to the feedback path for switching in different attenuation levels, based upon the control input of the mode selection switch identifying one or more of multiple potential operating modes. Operation of the multimode transmit power control loop increases or decreases an operating level of amplified power output from the power amplifier, which is proportional to a present level of attenuation resulting from the particular impedance circuit being applied to the feedback path via the mode selection switch.

A semiconductor device includes a differential amplification circuit that outputs differential output signals Vo1 and Vo2, external output terminals PD1 and PD2 to which one of the differential output signals Vo1 and Vo2 and single end signals Vo3 and Vo4 is selectively supplied, switch units SW1 and SW2 that control a conduction state between the external output terminal PD1 and the feedback line and a conduction state between the external output terminal PD2 and the feedback line, respectively, resistance elements R1 and R2 respectively provided in series with the switch units SW1 and SW2, a CMFB circuit that controls a common mode voltage of the differential amplification circuit according to a difference between an intermediate voltage Vcm of the external output terminals PD1 and PD2 in the feedback line and a reference voltage Vref, and a switch unit SW3 that controls to supply a clamp voltage to the feedback line.

A semiconductor device includes a differential amplification circuit that outputs differential output signals Vo1 and Vo2, external output terminals PD1 and PD2 to which one of the differential output signals Vo1 and Vo2 and single end signals Vo3 and Vo4 is selectively supplied, switch units SW1 and SW2 that control a conduction state between the external output terminal PD1 and the feedback line and a conduction state between the external output terminal PD2 and the feedback line, respectively, resistance elements R1 and R2 respectively provided in series with the switch units SW1 and SW2, a CMFB circuit that controls a common mode voltage of the differential amplification circuit according to a difference between an intermediate voltage Vcm of the external output terminals PD1 and PD2 in the feedback line and a reference voltage Vref, and a switch unit SW3 that controls to supply a clamp voltage to the feedback line.

Systems and methods are provided for reducing the effects of an impedance mismatch between a communications system and a shared communications medium. A communication system, such as a transceiver within a cable modem, switches between various operating modes including a transmit mode, a receive mode, and a standby mode. The standby mode may be used while the transceiver is in an idle state between modes, such as while changing an amplifier gain states in between transmissions. While transitioning between modes, the impedance presented by the communications system can temporarily fluctuate causing unwanted signal reflections to propagate out of the communications system and on to the shared medium. Circuitry within the communications system, such as transmission circuitry including an adjustable attenuator, may be placed into a hybrid attenuation-isolation mode during the transition causing the magnitude of any unwanted signal reflections to be attenuated and reducing the impact on the shared medium.

Apparatus and methods for digitally-assisted feedback offset correction are provided herein. In certain configurations, an amplifier includes amplification circuitry for providing amplification to an input signal and chopping circuitry for compensating for an input offset voltage of the amplifier. Additionally, the amplifier further includes a digitally-assisted feedback offset correction circuit, which includes a chopping ripple detection circuit, a feedback-path chopping circuit, a digital correction control circuit, and an offset correction circuit. The chopping ripple detection circuit generates a detected ripple signal based on detecting an output ripple of the amplifier. Additionally, the feedback-path chopping circuit demodulates the detected ripple signal using the amplifier's chopping clock signal. The digital correction control circuit receives the demodulated ripple signal, which the digital correction control circuit uses to control a value of a digital offset control signal that controls an amount of input offset correction provided by the offset correction circuit.

An audio amplifier, including: at least a two stage amplifier configured to receive an input signal and output an amplified output signal, the at least a two stage amplifier including at least one stage amplifier and an output stage amplifier; and an auxiliary stage amplifier having an input coupled to an output of the at least one stage amplifier and an input of the output stage amplifier.

There is provided an operational amplifier which is operable as well when an operating voltage decreases without creating a range where a circuit would not operate or reducing circuit gain. High-pass filters 102-105 provide output signals therefrom to bias-set input nodes of differential amplifiers Gm1-Gm4 to a potential within a common-mode range in which the respective differential amplifiers Gm1-Gm4 are operable. In this manner, the respective differential amplifiers Gm1-Gm4 can be operated effectively regardless of the possible decrease in a supply voltage, enabling normal amplifying operation. In addition, reduction in gain due to the reduced operational voltage is avoided. Therefore, it is preferably applicable to the application where digital and analog circuits are loaded together on the same IC chip. When a high-pass filter is required at each input side of two- or more-stage differential amplifiers, a phase compensation method utilizing multiple paths is provided for a lower range of a phase margin created at the low frequency side, enabling normal amplitude operation.

Feedback methods and devices to reduce gain in RF amplifiers, more in particular LNAs, are disclosed. The described methods are based on providing feedback paths from the drain terminal of one of the LNA cascode transistors to the source terminal of the LNA input transistor, or from the gate terminal of the input transistor to the source terminal of the LNA input transistor. The disclosed methods can be combined with one another or with existing feedback methods to provide further flexibility and improved tradeoffs when designing LNAs for applications having different requirements.

An analog front-end architecture for a capacitive pressure sensor with a low-noise amplifier unit for amplification of sensor signals from the sensor. The amplifier unit includes first and second integrator units for integrating charges injected into input terminals of the amplifier unit and for outputting integrated charges to output terminals of the amplifier unit, a feedback unit, and a startup unit. The feedback unit reinjects integrated charges from the integrator unit into the input terminals of the amplifier unit. The startup unit is switchable between first and second switching states and is configured, in the first switching state, to route the charges injected into the input terminals past the first integrator unit into the second integrator unit and from the second integrator unit into the feedback unit, and, in the second switching state, to route charges injected into the input terminals directly into the first integrator unit.