Apparatus and methods for vector modulator phase shifters are provided. In certain embodiments, a phase shifter includes a quadrature filter that filters a differential input signal to generate a differential in-phase (I) voltage and a differential quadrature-phase (Q) voltage, an in-phase variable gain amplifier (I-VGA) that amplifies the differential I voltage to generate a differential I current, a quadrature-phase variable gain amplifier (Q-VGA) that amplifies the differential Q voltage to generate a differential Q current, and a current mode combiner that combines the differential I voltage and the differential Q voltage to generate a differential output signal. A phase difference between the differential output signal and the differential input signal is controlled by gain settings of the I-VGA and the Q-VGA.

A system may include a first input for receiving a first signal for driving an amplifier that drives a load, a second input for receiving a second signal driven by the amplifier, and an instability detector for detecting instability of a feedback loop for controlling the first signal based on comparison of the first signal and the second signal.

A peak detector for a power amplifier is provided that includes a threshold voltage detector configured to pulse a detection current in response to an amplified output signal from the amplifier exceeding a peak threshold. A plurality of such peak detectors may be integrated with a corresponding plurality of power amplifiers in a transmitter. Should any peak detector assert an alarm signal or more than a threshold number of alarm signals during a given period, a controller reduces a gain for the plurality of power amplifiers.

Technology for grouping, consolidating, and pairing individual playback devices with network capability (players) to stimulate a multi-channel listening environment is disclosed. An example method includes receiving an audio signal containing a range of audio frequencies; amplifying, according to a gain parameter, the audio signal to be reproduced by at least one speaker. The example method includes automatically increasing the gain parameter to a higher gain parameter responsive to a determination that no more than a subset of the range of audio frequencies is to be reproduced by the at least one speaker. The example method includes amplifying, according to the higher gain parameter, the audio signal containing no more than the subset of the range of audio frequencies to be reproduced by the at least one speaker.

An amplifier includes a first input transistor, a second input transistor, a first cascode transistor, a second cascode transistor, a first current mirror circuit, and a second current mirror circuit. The first input transistor is coupled to a first input terminal. The second input transistor is coupled to a second input terminal and the first input transistor. The first cascode transistor is coupled to the first input transistor. The second cascode transistor is coupled to the second input transistor and the first cascode transistor. The first current mirror circuit is coupled to the first cascode transistor, the second cascode transistor, and the first input terminal. The second current mirror circuit is coupled to the first cascode transistor, the second cascode transistor, and the second input terminal.

Embodiments of apparatus and method for digital variable gain adjustment (DVGA) are disclosed. In an example, a baseband chip includes an unpacking module, a symbol recording module operatively coupled to the unpacking module, and a first variable gain adjusting (VGA) module operatively coupled to the symbol recording module. The unpacking module is configured to unpack a plurality of symbols from a first representation of pseudo floating-point numbers to a second representation of fixed-point numbers. The symbol recording module is configured to obtain a symbol parameter based on the unpacking. The first VGA module is configured to dynamically adjust gains of the plurality of symbols having the second representation based on the symbol parameter.

The processing of audio signals is shown in which a first gain-adjustable amplifier is configured to receive a feed forward signal from an input and a second gain-adjustable amplifier is configured to receive a feedback signal from an output. A gain controller supplies a first gain control signal to the first gain-adjustable amplifier, wherein the gain controller supplies a complementary second gain control signal to the second gain-adjustable amplifier, which may be the reciprocal of the first gain control signal. A first combiner is arranged to combine a first output from the first gain-adjustable amplifier with a second output from the second gain-adjustable amplifier. A plurality of filter elements are configured in parallel, wherein each filter element receives an output from the first combiner. A second combiner combines outputs from the filter elements with the original input signal and the filter elements have mutually different filtering characteristic.

Disclosed herein are embodiments of a wide bandwidth attenuator circuit having a tunable gain and tunable input impedance. In some embodiments, the wideband attenuator circuit comprises a serial capacitor shunted to ground by a plurality of circuit slices that are connected in parallel and switchably coupled to the output node of the attenuator. Each circuit slice has a tunable resistor that can be set to a conductive state (“enabled”) or a high impedance state (“disabled”) The number of enabled circuit slices that are connected in parallel may be used to program the attenuator gain and the attenuator impedance.

Disclosed herein are embodiments of a wide bandwidth attenuator circuit having a tunable gain and tunable input impedance. In some embodiments, the wideband attenuator circuit comprises a serial capacitor shunted to ground by a plurality of circuit slices that are connected in parallel and switchably coupled to the output node of the attenuator. Each circuit slice has a tunable resistor that can be set to a conductive state (“enabled”) or a high impedance state (“disabled”) The number of enabled circuit slices that are connected in parallel may be used to program the attenuator gain and the attenuator impedance.

Methods, systems, and devices for delay adjustment circuits are described. Amplifiers (e.g., differential amplifiers) may act like variable capacitors (e.g., due to the Miller-effect) to control delays of signals between buffer (e.g., re-driver) stages. The gains of the amplifiers may be adjusted by adjusting the currents through the amplifiers, which may change the apparent capacitances seen by the signal line (due to the Miller-effect). The capacitance of each amplifier may be the intrinsic capacitance of input transistors that make up the amplifier, or may be a discrete capacitor. In some examples, two differential stages may be inserted on a four-phase clocking system (e.g., one on 0 and 180 phases, the other on 90 and 270 phases), and may be controlled differentially to control phase-to-phase delay.