Abstract: A DA-converter system comprises the cascade of a multi-bit sigma-delta modulator and a DA-converter. The quantization noise of the sigma-delta modulator is isolated, the isolated quantization noise is word-length reduced in a second noise shaper with frequency independent signal transfer function and the isolated word-length reduced quantization noise is subtracted from the quantization noise of said cascade. Preferably the isolated quantization noise is amplified before and attenuated after the second noise shaper.

Abstract: A digital volume control device comprises a logic unit for volume control of digital input signals. Successively supplied m-bits words with maximally k bits active, derived from the output signals of or supplied by a volume control (4) with a quantizer (5) element the filtered m-bits workds are passed, however, with only the j most significant active bits of these filtered signals. The noise shaper operates with a frequency that is a k/j-fold of the frequency by which the m-bits words are supplied. An up-sampler (3) is provided for operation frequency adjustment of the filtered m-bits words to the noise shaper. This operation frequency is at least a factor k/j greater than the sample rate of the digital input signals. The control signals for the logic unit are formed by the m-bits words passed by the quantizer.

Abstract: An analog-to-digital conversion arrangement for converting an analog input signal into a digital output signal with a most significant part and a least significant part comprises sample means for sampling the analog input signal, a plurality of coarse resolution analog-to-digital converters for converting the sampled analog input signal into a coarse digital signal representing the most significant part of the digital output signal, whereby the coarse resolution analog-to-digital converters are operated in an interleaved way. The analog-to-digital conversion arrangement further comprises a fine resolution analog-to-digital converter for converting the sampled analog input signal into a fine digital signal representing the least significant part of the digital output signal, based upon the coarse digital signal generated by any of said coarse resolution analog-to-digital converters.

Abstract: A circuit for analogue to digital or digital to analogue conversion comprising at least 2n matched current sources (40-1, 40-2, 40-n), where n is the resolution required of the conversion. Preferably more than 2n current sources (40-1, 40-2, 40-n) are used. The order in which the sources (40-1, 40-2, 40-n) are used may be changed in different samples. The current sources (40-1, 40-2, 40-n) may be replaced by one bit switched capacitor converters or by inverters connected to one end of a set of resistors, the other ends of which are connected to the virtual ground for an operational amplifier or alternatively to each other and arranged to directly generate the output voltage. According to one embodiment of the invention there is provided a sigma-delta analogue to digital converter comprising the circuit of the first aspect.