Programmable gain ADC
First Claim
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1. A programmable gain circuit for an analog-to-digital converter, comprising:
- a sampling capacitor for storing a sample of a voltage representative of an analog signal to be converted to a corresponding digital signal;
a comparator circuit for comparing said sampled voltage with a reference analog signal;
a digital-to-analog converter (DAC) for generating said reference analog signal; and
a switched capacitor circuit, including a plurality of switched capacitors coupled between an output of said DAC and an input circuit of said comparator, wherein a desired gain can be achieved as a function of a switched arrangement of said switched capacitors.
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Abstract
A programmable gain circuit for analog-to-digital converter. A switched capacitor network capacitively couples an analog reference from a DAC to a comparator so that the sampled amplitude of the input analog signal can be compared with said analog reference. The ratio of the capacitance of the sampling capacitor to that of the switched capacitor network establishes an effective gain to the analog signal being converted.
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Citations
21 Claims
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1. A programmable gain circuit for an analog-to-digital converter, comprising:
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a sampling capacitor for storing a sample of a voltage representative of an analog signal to be converted to a corresponding digital signal;
a comparator circuit for comparing said sampled voltage with a reference analog signal;
a digital-to-analog converter (DAC) for generating said reference analog signal; and
a switched capacitor circuit, including a plurality of switched capacitors coupled between an output of said DAC and an input circuit of said comparator, wherein a desired gain can be achieved as a function of a switched arrangement of said switched capacitors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of providing gain in an analog-to-digital converter circuit, comprising the steps of:
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coupling an analog signal amplitude via an input capacitor to a node;
coupling an analog reference via a switched capacitor network to said node;
comparing a voltage representative of the voltage of said node with a second voltage to produce a digital signal; and
switching a number of capacitors in said switched capacitor network to vary a capacitance thereof for adjusting the magnitude of the analog reference relative to the magnitude of the analog signal amplitude at said node. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A programmable gain circuit for an analog-to-digital converter, comprising:
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a comparator circuit for generating a digital signal as a function of voltages applied to inputs thereof;
at least one input capacitor for transferring an analog signal amplitude to a node for comparing by said comparator;
a digital-to-analog converter for generating a reference voltage as a function of a digital word input thereto; and
a switched capacitor network including a plurality of capacitors, and a plurality of switches for activating and deactivating ones of said switched capacitors, a first terminal of said switched capacitor network driven by said reference voltage, and a second terminal of said switched capacitor network driving said node, whereby for effective larger capacitances generated by said switched capacitor network a smaller reference voltage is required to drive said switched capacitor network to produce a voltage at said node substantially equal in magnitude to said analog signal amplitude, thereby effectively lowering the gain of said analog-to-digital converter. - View Dependent Claims (19, 20, 21)
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Specification