Methods, apparatus, systems, and articles of manufacture are disclosed to generate a modulation protocol to output audio. An example apparatus includes a modulation circuit including a first input, a second input, a first output, and a second output; a first gate coupled to the first output of the modulation circuit; a second gate coupled to the second output of the modulation circuit; a first multiplexer including a first input coupled to the first output of the modulation circuit, a second input coupled to the output of the second gate, and an output coupled to a first switch; and a second multiplexer including a first input coupled to the second output of the modulation circuit, a second input coupled to the output of the first gate, and an output coupled to a second switch.

Methods, apparatus, systems, and articles of manufacture are disclosed to generate a modulation protocol to output audio. An example apparatus includes a modulation circuit including a first input, a second input, a first output, and a second output; a first gate coupled to the first output of the modulation circuit; a second gate coupled to the second output of the modulation circuit; a first multiplexer including a first input coupled to the first output of the modulation circuit, a second input coupled to the output of the second gate, and an output coupled to a first switch; and a second multiplexer including a first input coupled to the second output of the modulation circuit, a second input coupled to the output of the first gate, and an output coupled to a second switch.

A semiconductor device includes a temperature-independent current generator that generates a reference current substantially independent of temperature and a mirror current that is a substantial duplicate of the reference current, a pulse signal generator that samples the mirror current so as to generate a pulse signal, and a counter that obtains a number of pulse signals generated by the pulse signal generator, that permits the pulse signal generator to generate a pulse signal when it is determined thereby that the number of pulse signals obtained thereby is less than a predetermined threshold value, and that inhibits the pulse signal generator from generating a pulse signal when it is determined thereby that the number of pulse signals obtained thereby is equal to the predetermined threshold value. A method for monitoring a temperature of the semiconductor device is also disclosed.

A sigma-delta ADC is described including a passive filter with an input coupled to the ADC input and a filter output. A gain stage has an input connected to the filter output. A quantiser has an input connected to the gain stage output and a quantiser output. The passive filter includes a first filter resistor between the filter input and the filter output and a filter capacitor having first terminal coupled to the filter output. A feedback resistor is coupled between the quantiser output and the filter output and receives a negative of the value of the output to provide negative feedback to the filter output. The gain stage has a capacitor and resistor in series, and a gain element connected to the gain stage input and an output connected to the gain stage output. One terminal of the gain stage capacitor is connected to the gain element output.

A method for a fast settling ripple reduction loop for high speed precision chopper amplifiers includes amplifying an input signal with a signal path to generate a first output, the signal path comprising chopping the input signal to generate a first chopper output, amplifying the first chopper output with an amplifier to generate an amplifier output and chopping the amplified output to generate a second chopper output. An output ripple of the first output is reduced with a Ripple Reduction Loop comprising chopping the second chopper output to generate a third chopper output, filtering the third chopper output with a filter to generate a Direct Current (DC) offset correction, and combining the DC offset correction with the amplifier output, wherein the third chopper output is driven to the output voltage of the filter and the RRL is disconnected from the low frequency signal path in response to a non-linear event.

A method for a fast settling ripple reduction loop for high speed precision chopper amplifiers includes amplifying an input signal with a signal path to generate a first output, the signal path comprising chopping the input signal to generate a first chopper output, amplifying the first chopper output with an amplifier to generate an amplifier output and chopping the amplified output to generate a second chopper output. An output ripple of the first output is reduced with a Ripple Reduction Loop comprising chopping the second chopper output to generate a third chopper output, filtering the third chopper output with a filter to generate a Direct Current (DC) offset correction, and combining the DC offset correction with the amplifier output, wherein the third chopper output is driven to the output voltage of the filter and the RRL is disconnected from the low frequency signal path in response to a non-linear event.

An amplifier including a P-channel transistor having current terminals coupled between a first node and a second node and having a control terminal coupled to a third node receiving an input voltage, an N-channel transistor having current terminals coupled between a fourth node developing an output voltage and a supply voltage reference and having a control terminal coupled to the second node, a first resistor coupled between the first node and a supply voltage, a second resistor coupled between the first and fourth nodes, and a current sink sinking current from the second node to the supply reference node. The amplifier may be converted to differential form for amplifying a differential input voltage. Current devices may be adjusted for common mode, and may be moved or added to improve headroom or to improve power supply rejection. Chopper circuits may be added to reduce 1/f noise.

An amplifier including a P-channel transistor having current terminals coupled between a first node and a second node and having a control terminal coupled to a third node receiving an input voltage, an N-channel transistor having current terminals coupled between a fourth node developing an output voltage and a supply voltage reference and having a control terminal coupled to the second node, a first resistor coupled between the first node and a supply voltage, a second resistor coupled between the first and fourth nodes, and a current sink sinking current from the second node to the supply reference node. The amplifier may be converted to differential form for amplifying a differential input voltage. Current devices may be adjusted for common mode, and may be moved or added to improve headroom or to improve power supply rejection. Chopper circuits may be added to reduce 1/f noise.

A current sensor architecture is implemented using a trans-resistance amplifier circuit having a low pass filter characteristic. The current sensing resistor and the input resistors for the amplifier circuit are matched thermally so that they have substantially identical temperature coefficients. The feedback resistors, which are coupled in parallel with corresponding capacitors, are implemented using switched capacitor circuits that emulate resistors. With this configuration, the current sensor is temperature insensitive.

A current sensor architecture is implemented using a trans-resistance amplifier circuit having a low pass filter characteristic. The current sensing resistor and the input resistors for the amplifier circuit are matched thermally so that they have substantially identical temperature coefficients. The feedback resistors, which are coupled in parallel with corresponding capacitors, are implemented using switched capacitor circuits that emulate resistors. With this configuration, the current sensor is temperature insensitive.