The present invention discloses an audio processing circuit, wherein when the audio processing circuit determines that a signal being processed is a small signal, an output stage uses a regulated supply voltage provided by a voltage regulator, and the output stage uses an open-loop structure to reduce noise of an output audio signal; and when the audio processing circuit determines that the signal being processed is a large signal, the output stage directly uses the supply voltage without using the regulated supply voltage, and the output stage uses a closed-loop structure to reduce the total harmonic distortion of the output audio signal. By using the present invention, the audio processing circuit can have a good performance indicator with a small chip area design.

Methods and devices to support multiple gain states in amplifiers are described. The methods and devices are based on implementing a feedback element in the amplifier and adjusting the impedance of the feedback element to provide a desired gain while maintaining the overall performance of the amplifier and reducing degradation of the S12 parameter. The feedback element includes an adjustable attenuator and a tunable resistive element. The adjustable attenuator is provided in a path that is common to the feedback path and the bypass path of the amplifier. Exemplary implementations of adjustable attenuators are also presented.

A switched-capacitor circuit comprising a differential operational amplifier and a feedback circuit is described. In some embodiments, the feedback circuit may be configured to provide a reference voltage that is insensitive to temperature and/or process variations. In some embodiments, the feedback circuit may be configured to mitigate the time delay associated with one or more capacitors of the switched-capacitor circuit. The switched-capacitor circuit may be controlled by a pair of control signals. During a first phase, one or more capacitors may be charged, or discharged, through an input signal. During a second phase, the electric charge of the one or more capacitors may be retained.

An apparatus includes an input amplifier stage and a switch that has a first terminal at a virtual ground input of the input amplifier stage.

A switched-capacitor circuit comprising a differential operational amplifier and a feedback circuit is described. In some embodiments, the feedback circuit may be configured to provide a reference voltage that is insensitive to temperature and/or process variations. In some embodiments, the feedback circuit may be configured to mitigate the time delay associated with one or more capacitors of the switched-capacitor circuit. The switched-capacitor circuit may be controlled by a pair of control signals. During a first phase, one or more capacitors may be charged, or discharged, through an input signal. During a second phase, the electric charge of the one or more capacitors may be retained.

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.

A voltage reference buffer circuit, including: an amplifier having input terminals and output terminals; a plurality of current sources coupled to the input terminals of the amplifier, the plurality of current sources including a plurality of degeneration resistors coupled to a first plurality of voltage supplies; and a degeneration resistor chopping module comprising a first and second plurality of switches coupled to the plurality of degeneration resistors.

An apparatus includes an input amplifier stage and a switch that has a first terminal at a virtual ground input of the input amplifier stage.

A circuit for generation of a reference voltage for an electronic system, which circuit comprises at least one digital buffer (U21, U31, U32, U41, U51), a low pass filter (R21, C21; R31, C31; R41, C41; R51, C51) and an operational amplifier (OA21, OA31, OA41, OA51)), which circuit is adapted to revive an input in the form of a bandgap reference voltage into the digital buffer, which digital buffer is adapted to receive a digital input from a Pulse Width Modulated (PWM) signal, which digital buffer is adapted to generate an output signal adapted to be fed to the low pass filter, which output signal after filtration is adapted to be fed to a positive input terminal of the operational amplifier, which operational amplifier comprises a feedback circuit, which feedback circuit comprises at least one capacitor (C22, C32, C44, C54) adapted to be connected from an output terminal of the operational amplifier towards a negative input terminal of the operational amplifier so as to form an integrator, wherein the feedback circuit further comprises at least one chopped signal path (R22, S21; R33, R34, S32; R33, R35, C35, S31), which chopped signal is adapted to be modulated by the output signal of the digital buffer.

The present disclosure provides for transimpedance amplifiers for crossbar circuits. A crossbar circuit may include a plurality of bit lines intersecting with a plurality of word lines and a plurality of cross-point devices. Each of the plurality of the cross-point devices is connected to at least one of the word lines and at least one of the bit lines. The crossbar circuit may further include a transimpedance amplifier to generate an output voltage representative of a sum of currents flowing through a first bit line of the plurality of bit line. The transimpedance amplifier may include an operational amplifier, a current mirror circuit connected to an output of the operational amplifier, and one or more resistors connected to the current mirror circuit and a supply voltage.