Current mirror and current cancellation circuit
First Claim
1. A method comprising:
- receiving a first current source current at a first node;
receiving a first current mirror reference current from a first current mirror through a first switch at the first node, the first switch coupled to the first node and having a switch configuration comprising at least one of an open configuration or a closed configuration;
receiving a signal second current mirror reference current from a second current mirror through a second switch at a second node, the second switch coupled to the second node and having the switch configuration;
controlling the switch configuration of the first switch and the second switch via a discrete pulse density modulated output generated by a sigma delta modulator, 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 discrete pulse density modulated output represents a first current source current as a function of the first current mirror current;
receiving a second current source current at the second node,wherein the second current mirror reference current subtracts at least a portion of the second current source current at the second node.
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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.
26 Citations
5 Claims
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1. A method comprising:
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receiving a first current source current at a first node; receiving a first current mirror reference current from a first current mirror through a first switch at the first node, the first switch coupled to the first node and having a switch configuration comprising at least one of an open configuration or a closed configuration; receiving a signal second current mirror reference current from a second current mirror through a second switch at a second node, the second switch coupled to the second node and having the switch configuration; controlling the switch configuration of the first switch and the second switch via a discrete pulse density modulated output generated by a sigma delta modulator, 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 discrete pulse density modulated output represents a first current source current as a function of the first current mirror current; receiving a second current source current at the second node, wherein the second current mirror reference current subtracts at least a portion of the second current source current at the second node. - View Dependent Claims (2, 3, 4, 5)
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Specification