An audio processing circuit includes a cascade operational amplifier circuit, an output node, and a pull-down circuit. The cascade operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit. The first operational amplifier circuit includes a main operational amplifier and a secondary operational amplifier that are connected in parallel. The pull-down circuit is configured to pull down a voltage at the output node after the first operational amplifier circuit is turned on. The second operational amplifier circuit is configured to, after the secondary operational amplifier is turned on, control a voltage gain of the secondary operational amplifier to change gradually from low to high.

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.

Methods, systems, and circuities for selectively connecting an RF signal to front end circuitry and selectively attenuating the RF signal are disclosed. In one example, an interface circuitry includes switching circuitry and attenuator circuitry. The switching circuitry is connected in series between an output of an amplifier and a front end circuitry configured to transmit a radio frequency (RF) signal output by the amplifier. The switching circuitry connects the output of the amplifier to a selected one or more front end circuitry inputs to create one or more signal paths. The attenuator circuitry is connected between the output of the amplifier and ground to create an attenuation path in a shunt configuration relative to the one or more signal paths. The attenuator circuitry is configured to attenuate the RF signal.

A switched-capacitor power amplifier comprising a plurality of cells and methods for its operation are described. Switched signal lines switch supply to respective capacitors. Switches connect respective signal lines to a first supply and switches connect respective signal lines to a second supply. Pairs of switches on each signal line are switched so that one is switched off whilst the other is switched on. In a full amplitude mode, operation of the switches provides an output having a peak determined by the first supply. A switch signal line is provided between nodes in respective signal lines, a switch being provided in the switch signal line. In a half amplitude mode, switch is switched at the radio frequency in the other direction to that of switches connecting the signal lines to respective ones of the first and second supplies with the other switches being kept open.

A semiconductor device in which variations are controlled is provided. The semiconductor device has a function of converting a digital signal into an analog signal, and includes a digital-analog converter circuit, an amplifier circuit, first to fourth switches, a first output terminal, a second output terminal, and a power source. The amplifier circuit is configured to perform feedback control when the first switch and the fourth switch are on and the second switch and the third switch are off. The amplifier circuit is configured to perform comparison control when the first switch and the fourth switch are off and the second switch and the third switch are on; utilizing this, variations in the digital-analog converter circuit and the amplifier circuit are controlled.

A high frequency circuit includes a transmit terminal and a transmit and receive terminal, a power amplifier that amplifies a high frequency signal inputted from the transmit terminal and outputs the high frequency signal toward the transmit and receive terminal, and an output matching circuit that is positioned on a signal path connecting the power amplifier and the transmit and receive terminal and that optimizes the output load impedance of the power amplifier. The output matching circuit includes a matching circuit coupled to an output terminal of the power amplifier, another matching circuit, and a switch that changes a connection between the matching circuits. The power amplifier and the switch are formed at a single semiconductor IC. The matching circuits are formed outside the semiconductor IC.

An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common-mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

An electronic device is provided The electronic device includes a patch antenna element, at least one antenna including a first feeding unit electrically connected to the patch antenna element and a second feeding unit electrically connected to the patch antenna element so as to have a designated isolation for a signal that is input to the first feeding unit, a radio frequency integrated circuit (RFIC) which includes a first communication circuit including a first transmission circuit and a first reception circuit which are electrically connected to the first feeding unit, and a second communication circuit including a second transmission circuit and a second reception circuit which are electrically connected to the second feeding unit, and a processor.

An output driver with programmable single-ended and differential outputs includes a first switch, a first output attenuator, and a programmable attenuator. The first switch is coupled in a shunt configuration to a first path of a differential output of a first amplifier. The first output attenuator is included in the first path and is coupled to the first switch in accordance with the shunt configuration. The programmable attenuator is included in a second path of the differential output of the first amplifier.

A half-power buffer amplifier includes an amplification unit including first and second nodes, the amplification unit configured to differentially amplify a differential input signal and to output a differentially amplified output signal, a first output unit including a first buffer unit between a first power source having a first voltage and a second power source having a second voltage, a second buffer unit between the first and second power sources, and a first switch unit between the first and second buffer units, and a second output unit including a third buffer unit between the second power source and a third power source having a third voltage, a fourth buffer unit between the second and third power sources, and a second switch unit between the third and fourth buffer units. Each of the first to third buffer units receives the differentially amplified output signal. The first switch unit is turned on or off based on or in response to a pre-driving control signal.