Disclosed herein is a device and method for intelligently reducing power consumption in an audio amplifier in the device, and in particular Class-D amplifiers, through the use of metadata associated with settings of the playback device and/or content to be played on the playback device. The device includes components for analyzing the settings and content metadata and regulates the voltage provided to the audio amplifier based on this analysis.

Disclosed herein is a device and method for intelligently reducing power consumption in an audio amplifier in the device, and in particular Class-D amplifiers, through the use of metadata associated with settings of the playback device and/or content to be played on the playback device. The device includes components for analyzing the settings and content metadata and regulates the voltage provided to the audio amplifier based on this analysis.

A logarithmic amplifier includes a logarithmic current preamplifier circuit and logarithmic amplifier circuit. The logarithmic current preamplifier circuit includes an inverting input terminal, an output terminal, and a first diode. The first diode is coupled between the inverting input terminal of the logarithmic current preamplifier circuit and the output terminal of the logarithmic current preamplifier circuit. The logarithmic amplifier circuit includes an inverting input terminal, an output terminal, and a second diode. The inverting input terminal of the logarithmic amplifier circuit is coupled to the output terminal of the logarithmic current preamplifier circuit. The second diode is coupled between the inverting input terminal of the logarithmic amplifier circuit and the output terminal of the logarithmic amplifier circuit.

A logarithmic amplifier includes a logarithmic current preamplifier circuit and logarithmic amplifier circuit. The logarithmic current preamplifier circuit includes an inverting input terminal, an output terminal, and a first diode. The first diode is coupled between the inverting input terminal of the logarithmic current preamplifier circuit and the output terminal of the logarithmic current preamplifier circuit. The logarithmic amplifier circuit includes an inverting input terminal, an output terminal, and a second diode. The inverting input terminal of the logarithmic amplifier circuit is coupled to the output terminal of the logarithmic current preamplifier circuit. The second diode is coupled between the inverting input terminal of the logarithmic amplifier circuit and the output terminal of the logarithmic amplifier circuit.

A method for inducing brain waves by sound has the following steps: receiving a first channel input signal and a second channel input signal; adjusting a volume gain of the first channel input signal to form a first channel output signal, wherein a format of the volume gain of the first channel output signal is a first wave format; adjusting a volume gain of the second channel input signal to form a second channel output signal, wherein a format of the volume gain of the second channel output signal is a second wave format, wherein there is a phase difference between the first wave format and the second wave format, wherein the formats of the first wave format and the second wave format are the same; outputting the first channel output signal to a first speaker; and outputting the second channel output signal to a second speaker.

A method for inducing brain waves by sound has the following steps: receiving a first channel input signal and a second channel input signal; adjusting a volume gain of the first channel input signal to form a first channel output signal, wherein a format of the volume gain of the first channel output signal is a first wave format; adjusting a volume gain of the second channel input signal to form a second channel output signal, wherein a format of the volume gain of the second channel output signal is a second wave format, wherein there is a phase difference between the first wave format and the second wave format, wherein the formats of the first wave format and the second wave format are the same; outputting the first channel output signal to a first speaker; and outputting the second channel output signal to a second speaker.

A signal processor and method. The signal processor includes a signal current path. The signal processor includes a transconductor. The transconductor has an input operable to receive an input voltage of the signal processor. The transconductor also has an output operable to output a current based on the input voltage. The signal processor also includes a processing stage coupled to the output of the transconductor to receive and process the current outputted by the transconductor. The signal processor further includes a current replicator operable to generate a replica current proportional to the current outputted by the transconductor. The signal processor also includes a comparator operable to compare an output of the current replicator with a reference. The signal processor further includes a current limiter operable to limit the current outputted by the transconductor based on the comparison of the output of the current replicator with the reference.

Provided is an analog switch circuit that allows switching between an on-state and an off-state according to a control signal, the analog switch circuit including a main input terminal that receives an input voltage, an output terminal, an upper-side power supply terminal that receives an upper supply voltage, a lower-side power supply terminal that receives a lower supply voltage, a main N-channel MOS transistor and a main P-channel MOS transistor that are disposed in parallel between the main input terminal and the output terminal, and a controller that includes a voltage generating circuit that generates a high-side voltage according to the upper supply voltage and the input voltage and a low-side voltage according to the input voltage and the lower supply voltage. The controller can control a gate and a back gate of each of the main N-channel and P-channel MOS transistors based on the high-side and low-side voltages.

Provided is an analog switch circuit that allows switching between an on-state and an off-state according to a control signal, the analog switch circuit including a main input terminal that receives an input voltage, an output terminal, an upper-side power supply terminal that receives an upper supply voltage, a lower-side power supply terminal that receives a lower supply voltage, a main N-channel MOS transistor and a main P-channel MOS transistor that are disposed in parallel between the main input terminal and the output terminal, and a controller that includes a voltage generating circuit that generates a high-side voltage according to the upper supply voltage and the input voltage and a low-side voltage according to the input voltage and the lower supply voltage. The controller can control a gate and a back gate of each of the main N-channel and P-channel MOS transistors based on the high-side and low-side voltages.

Systems and methods for measurement of signal power, when the signal is substantially variable or otherwise time varying. A log-linear VGA is coupled in a feedback configuration to a difference-of-squares detector and an integrator. The log-linear VGA includes a set of selectable amplifier cells. A sliding current generator selects one or more amplifier cells, wholly or partially, producing a sum of outputs. Some of the selectable amplifier cells have differential amplification, while others have similar amplification but are differentially attenuated. Switches turn off to isolate amplifier cells when the cell is not selected. Canceling circuits produce an output opposite to unselected amplifier cells, providing a sum near zero. Temperature compensation and other adjustment include two components: when the output y and the input x have the relation y=a+b log x the log-linear VGA can adjust either the offset or slope.