Low power loss current digital-to-analog converter used in an implantable pulse generator
First Claim
1. An implantable stimulator device, comprising:
- a first load having a first end and a second end, the first end of the first load coupled to a first power supply and the second end of the first load coupled to a first current generator configured to supply a fixed reference current to the second end of the first load;
a second load having a first end and a second end, the first end of the second load coupled to the first power supply;
a first transistor for providing an output current to a first electrode implantable adjacent to tissue to be stimulated, the first transistor coupled to the second end of the second load, the second load and the first transistor comprising an output path for the output current to the first electrode; and
a first feedback circuit for controlling the first transistor in accordance with at least a first voltage taken on the output path.
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Accused Products
Abstract
In one embodiment, the present invention provides an implantable stimulation device that includes output current sources and/or sinks configured to provide an output current for a load (i.e., tissue). The output path of the output current source or sink comprises a transistor which operates in a linear mode instead of a saturation mode. Because operation in a linear mode results in smaller drain-to-source voltage drops, power consumption in the output current source or sink (and hence in the implantable stimulator) is reduced, reducing battery or other power source requirements. Operation in the linear mode is facilitated in useful embodiments by a load in an input path (into which a reference current is sent) and a load in the output path (which bears the output current). The loads can be active transistors or passive resistors. A feedback circuit (e.g., an operational amplifier) receives voltages that build up across these loads, and sends a control signal to the gate of the transistor to ensure its linear operation.
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Citations
25 Claims
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1. An implantable stimulator device, comprising:
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a first load having a first end and a second end, the first end of the first load coupled to a first power supply and the second end of the first load coupled to a first current generator configured to supply a fixed reference current to the second end of the first load; a second load having a first end and a second end, the first end of the second load coupled to the first power supply; a first transistor for providing an output current to a first electrode implantable adjacent to tissue to be stimulated, the first transistor coupled to the second end of the second load, the second load and the first transistor comprising an output path for the output current to the first electrode; and a first feedback circuit for controlling the first transistor in accordance with at least a first voltage taken on the output path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification