Various aspects of this disclosure describe reducing distortion of a power amplifier by coupling a common mode signal, such as determined from a voltage supply signal of the power amplifier or output of the power amplifier, to an input of the power amplifier. A resistive digital-to-analog converter (DAC) can be coupled to the power amplifier, and a common mode signal is modulated onto differential reference voltages of the DAC, causing the common mode signal to exist at both the input and output of the power amplifier at approximately the same time. Consequently, current flowing at differential inputs of the power amplifier due to the common mode component drops to zero, causing distortions due to common mode to differential mode conversion to be reduced.

In a semiconductor device according to related art, it is impossible to sufficiently correct an input offset of an operational amplifier. According to one embodiment, a semiconductor device calculates, when a voltage level of an output signal output in a state in which an input of the operational amplifier is short-circuited is determined, a correction code that adjusts the input offset of the operational amplifier based on a voltage level of an output signal determined based on a comparator circuit in a period during which the input offset is large and an output of the operational amplifier is close to a power supply voltage level or a ground voltage level and a correction code that adjusts the input offset of the operational amplifier based on a voltage level of an output signal determined based on an analog-to-digital conversion circuit in a period during which the input offset is small and the output of the operational amplifier is in an intermediate level between the power supply voltage and the ground voltage.

A circuit comprises: a circuit input; a circuit output; at least one passive feedback loop coupled between the circuit output and the circuit input; an active element, coupled in a feed-forward path of the circuit between the circuit input and the circuit output and configured to drive the at least one feedback loop in order to establish a function of the circuit, wherein the feed-forward path of the circuit comprises a second node (Vx) and a first node which are internal nodes of the active element and which are coupled between the circuit input and the circuit output, wherein the first node is configured to have a first voltage, the first voltage being a function of the circuit output, wherein the active element comprises a first voltage drop element coupled between the second node (Vx) and the first node.

A circuit includes an active balun having an RF signal input and having differential signal outputs, the active balun including a first pair of transistors coupled to the RF signal input, the first pair of transistors including a first transistor of a first type and a second transistor of a second type, wherein the first type and second type are complementary; and an intermodulation distortion (IMD) sink circuit having an operational amplifier (op amp) coupled between a first node and a second node, wherein the first transistor and second transistor are coupled in series between the first node and the second node.

A receiver includes a signal receiving part suitable for outputting a signal corresponding to a reception signal that is received through an input terminal, and controlling a DC voltage of a signal to be outputted, according to an offset signal, an amplifying part suitable for amplifying and outputting an output of the signal receiving part, and a feedback control part suitable for controlling the offset signal according to an output of the amplifying part.

A circuit for implementing a differential input receiver is described. The circuit comprises an input circuit having a first input node and a second input node configured to receive a differential input signal; a first output circuit having a first capacitor coupled between the first input node and a first output node and a second capacitor coupled between the second input node and a second output node, wherein the first output circuit generates an output signal at the first output and the second output when the input signal is in a first frequency range; and a second output circuit comprising an amplifier having a first amplifier input coupled to the first input node and a second amplifier input coupled to the second input node, wherein the second output circuit generates an output signal when the input signal is in a second frequency range which extends lower than the first frequency range. A method of implementing a differential input receiver is also described. The circuits and methods also allow for offset compensation.

A compensation circuit of a power amplifier includes a varactor, a voltage sensor and a control circuit. The varactor is coupled to an input terminal of the power amplifier. The voltage sensor is arranged for detecting an amplitude of an input signal of the power amplifier to generate a detecting result. The control circuit is coupled to the varactor and the voltage sensor, and is arranged for controlling a bias voltage of the varactor to adjust a capacitance of the varactor according to the detecting result.

Apparatus and methods for a difference amplifier are provided. In certain examples, the difference amplifier can provide high common mode rejection without differential signal attenuation. In an example, a difference amplifier circuit can include first and second amplifiers, first and second buffer amplifiers, a first feedback voltage divider coupled between an output of the first buffer amplifier and an output of the second amplifier, and a second feedback voltage divider coupled between an output of the second buffer amplifier and an output of the first amplifier.

Apparatus and methods for a difference amplifier are provided. In certain examples, the difference amplifier can provide high common mode rejection without differential signal attenuation. In an example, a difference amplifier circuit can include first and second amplifiers, first and second buffer amplifiers, a first feedback voltage divider coupled between an output of the first buffer amplifier and an output of the second amplifier, and a second feedback voltage divider coupled between an output of the second buffer amplifier and an output of the first amplifier.

A compensation circuit of a power amplifier includes a varactor, a voltage sensor and a control circuit. The varactor is coupled to an input terminal of the power amplifier. The voltage sensor is arranged for detecting an amplitude of an input signal of the power amplifier to generate a detecting result. The control circuit is coupled to the varactor and the voltage sensor, and is arranged for controlling a bias voltage of the varactor to adjust a capacitance of the varactor according to the detecting result.