A/D converter input stage

Abstract

There is described an input stage for an A / D converter, comprising (a) a transconductance element (306, 406) adapted to receive, at a first input (302, 402) of the transconductance element, an analog input signal that is to be converted to a digital signal by the A / D converter, (b) a feedback path for providing an analog feedback signal to a second input (304, 404) of the transconductance element, the analog feedback signal being based on a digital output signal of the A / D converter, and (c) an integrator (308, 408) for integrating an output current of the transconductance element, wherein the integrating element is adapted to generate an integrator output signal representative of the integrated output current. There is also described an A / D converter comprising such an input stage and a system comprising a plurality of such A / D converters.

Description

technical field [0001] The present application relates to the field of analog-to-digital converters, in particular input stages for such converters. Background technique [0002] In an A / D converter (analog-to-digital converter), the input stage is usually the most critical part of the converter related to noise and linearity. To improve linearity, degeneration of the input transistor pair is often used, but this also increases noise. Another solution is to use an input stage that has feedback to the input of the amplifier (like an inverting amplifier), but requires an input resistor, so the input impedance of the A / D converter will be limited, but this is not Desirable, especially undesirable when an A / D converter needs to interface with a sensor. Also, this feedback increases power consumption. [0003] Additionally, in sensor applications, it is often required that the signal processing path provide sufficient gain matching between the different channels. For example,...

AI Technical Summary

Problems solved by technology

The disadvantage of this implementation is that both transconductance elements have to convert the full-swing signal (either the input signal or the DA converter output signal), which requires a higher linearity level to avoid distortion

Usually linearity is obtained by the degeneration of the transconductance stage, but obviously this will increase the noise (due to the added resistance), therefore, need to increase the power to achieve the required noise level

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