Sigma-delta analog-to-digital converter
First Claim
1. A method, comprising:
- receiving, by a current mirror, an input current from a working electrode of an electrochemical sensor, wherein the current mirror comprises a first current path between a voltage supply and the working electrode, a second current path between the voltage supply and a capacitor, a first field-effect transistor and a second field-effect transistor connected in series in the first current path, and a third field-effect transistor and a fourth field-effect transistor connected in series in the second current path;
developing, by the current mirror, a mirror current that mirrors the input current;
providing, by a current source, a control current based on a waveform;
developing, by the capacitor, a capacitor voltage in response to at least the mirror current and control current;
generating, by a comparator, the waveform based on variations of the capacitor voltage relative to a comparison voltage; and
providing, by a counter, a digital output based on a number of times a particular feature in the waveform occurs during a predetermined sampling period.
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Accused Products
Abstract
A potentiostat includes a voltage regulator, a current mirror, a capacitor, a comparator, a current source, and a counter. The voltage regulator maintains a voltage on a working electrode of an electrochemical sensor. The current mirror develops a mirror current that mirrors an input current from the working electrode. The capacitor is alternately charged by the mirror current, causing the capacitor voltage to increase at a rate related to the current'"'"'s magnitude, and discharged by a control current, causing the capacitor voltage to decrease. The comparator outputs a waveform that includes upward and downward transitions based on the variations of the capacitor voltage. The current source produces the control current based on the waveform. The counter counts the number of upward or downward transitions in the waveform during a predetermined sampling period to produce a digital output. The digital output is representative of the magnitude of the input current.
9 Citations
8 Claims
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1. A method, comprising:
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receiving, by a current mirror, an input current from a working electrode of an electrochemical sensor, wherein the current mirror comprises a first current path between a voltage supply and the working electrode, a second current path between the voltage supply and a capacitor, a first field-effect transistor and a second field-effect transistor connected in series in the first current path, and a third field-effect transistor and a fourth field-effect transistor connected in series in the second current path; developing, by the current mirror, a mirror current that mirrors the input current; providing, by a current source, a control current based on a waveform; developing, by the capacitor, a capacitor voltage in response to at least the mirror current and control current; generating, by a comparator, the waveform based on variations of the capacitor voltage relative to a comparison voltage; and providing, by a counter, a digital output based on a number of times a particular feature in the waveform occurs during a predetermined sampling period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification