Current mirror and current cancellation circuit
First Claim
1. A circuit comprising:
- a first node and a second node;
a first switch and a second switch, the first switch coupled to the first node and having an open configuration and a closed configuration, the second switch coupled to the second node and having an open configuration and a closed configuration;
a first current mirror and a second current mirror, the first current mirror coupled to the first switch and configured to provide a first current mirror current, the second current mirror coupled to the second switch and configured to provide a second current mirror current;
a sigma delta modulator having an input and an output, the input coupled to the first node and the output coupled to the first switch and the second switch, the output configured to provide a discrete pulse density modulated output to control the open configuration and the closed configuration of the first switch and the second switch, the discrete pulse density modulated output represents a first current source current as a function of the first current mirror current,wherein the second current mirror current subtracts at least a portion of a second current source current at the second node when the second switch is in the closed configuration.
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Abstract
Techniques are described to mirror currents and subtract currents accurately. In an implementation, a circuit includes a first current source coupled to a first node to provide a current IPD1 and a current mirror coupled to the first node through a first switch T1 to provide a current IREF1. In a closed configuration, the current IREF1 flows from the current mirror into the first node. A sigma delta modulator controls the switch T1 such that over a period of time an average current flowing from the current mirror into the first node is equal to the current IPD1 flowing out of the first node. The sigma delta modulator generates a digital output to control switch T2 to allow a current IREF2 into a second node, thus subtracting a portion of a current IPD2 at the second node over a period of time.
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Citations
7 Claims
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1. A circuit comprising:
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a first node and a second node; a first switch and a second switch, the first switch coupled to the first node and having an open configuration and a closed configuration, the second switch coupled to the second node and having an open configuration and a closed configuration; a first current mirror and a second current mirror, the first current mirror coupled to the first switch and configured to provide a first current mirror current, the second current mirror coupled to the second switch and configured to provide a second current mirror current; a sigma delta modulator having an input and an output, the input coupled to the first node and the output coupled to the first switch and the second switch, the output configured to provide a discrete pulse density modulated output to control the open configuration and the closed configuration of the first switch and the second switch, the discrete pulse density modulated output represents a first current source current as a function of the first current mirror current, wherein the second current mirror current subtracts at least a portion of a second current source current at the second node when the second switch is in the closed configuration. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification