Abstract: The present invention relates to battery power peripheral devices such as MP3 players which are also periodically connected to another power source such as a mains wall socket or USB cable power bus. In particular, but not exclusively, the present invention relates to regulation of these voltage sources. In general terms the present invention provides a multiple supply rail for the load regulators of a power supply circuit for a battery powered device. One supply rail is coupled to the battery, and another is coupled to a non-battery source such as an external mains regulated source and/or a bus power wire from a USB cable or similar. The regulators have multiple inputs, each for taking their input voltage from one of these supply rails.

Abstract: A signal amplifying circuit and associated methods and apparatuses, the circuit comprising: a signal path extending from an input terminal to an output terminal, a gain controller arranged to control the gain applied along the signal path in response to a control signal; an output stage within the signal path for generating the output signal, the output stage having a gain that is substantially independent of its supply voltage, and a variable voltage power supply comprising a charge pump for providing positive and negative output voltages, the charge pump comprising a network of switches that is operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage.

Abstract: The present invention relates to digital to analog converters, and especially but not exclusively to switched capacitor digital to analog converters (DACs) for digital audio signals. The present invention provides a switched capacitor DAC for converting a digital signal and comprising a feedback capacitor coupled between an input and an output of an operational amplifier; a charging capacitor and a switching arrangement arranged during a charging period to couple a first side of said charging capacitor to a first reference voltage or a second reference voltage dependent on said digital signal, the switching arrangement further arranged during said charging period to couple a second side of the charging capacitor to the second reference voltage or the first reference voltage in anti-phase to the reference voltage coupled to said first side of the charging capacitor; the switching arrangement further arranged during a settling period to couple said charging capacitor to said feedback capacitor.

Abstract: The present invention relates to battery power peripheral devices such as MP3 players which are also periodically connected to another power source such as a mains wall socket or USB cable power bus. In particular, but not exclusively, the present invention relates to regulation of these voltage sources. In general terms the present invention provides a multiple supply rail for the load regulators of a power supply circuit for a battery powered device. One supply rail is coupled to the battery, and another is coupled to a non-battery source such as an external mains regulated source and/or a bus power wire from a USB cable or similar. The regulators have multiple inputs, each for taking their input voltage from one of these supply rails.

Abstract: The present invention relates to battery power peripheral devices such as MP3 players which are also periodically connected to another power source such as a mains wall socket or USB cable power bus. In particular, but not exclusively, the present invention relates to regulation of these voltage sources. In general terms the present invention provides a dual supply rail for the load regulators of a power supply circuit for a battery powered device. One supply rail is coupled to the battery, and the other is coupled to a non-battery source such as an external mains regulated source and/or a bus power wire from a USB cable or similar. The regulators have dual inputs, each for taking their input voltage from one of these supply rails.

Abstract: This invention is generally concerned with digital-to-analogue converters and more particularly relates to techniques for reducing signal dependent loading of reference voltage sources used by these converters. A differential switched capacitor digital-to-analogue (DAC) circuit (500) comprises first and second differential signal circuit portions (500a,b) for providing respective positive and negative signal outputs with respect to a reference level, and has first and second reference voltage inputs (112,114) for receiving respective positive and negative references. Each of said first and second circuit portions comprises an amplifier (102a,b) with a feedback capacitor (104a,b), a second capacitor (106a,b), and a switch (108a,b, 110a,b) to switchably couple said second capacitor to a selected one of said reference voltage inputs to charge the second capacitor and to said feedback capacitor to share charge with the feedback capacitor.