Oximeter with nulled op-amp current feedback
First Claim
1. A method of producing a diode drive current in an oximeter, comprising:
- sensing at least a part of a current passing through the diode and converting the sensed current to sensed voltage;
inputting the sensed voltage to a feedback amplifier for stabilizing the current passing through the diode; and
eliminating an offset voltage across inputs of the feedback amplifier by charging and discharging a first capacitor connected to one of the inputs of the feedback amplifier.
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Accused Products
Abstract
A method of producing a diode drive current in an oximeter includes sensing at least a part of a current passing through the diode and converting the sensed current to a sensed voltage, inputting the sensed voltage to a feedback amplifier for stabilizing the current passing through the diode, and eliminating an offset voltage across inputs of the feedback amplifier. A pulse oximeter includes a diode for emitting light flashes, a feedback amplifier having inputs, a feedback capacitor, and an output, the feedback amplifier stabilizing a current passing through the diode, a nulling amplifier having inputs, a nulling capacitor, and an output, the nulling amplifier charging and discharging the feedback capacitor until the inputs of the feedback amplifier are at a same voltage. The operation may include synchronizing an elimination of input offset voltages of the feedback and nulling amplifiers with on or off state of diode current.
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Citations
26 Claims
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1. A method of producing a diode drive current in an oximeter, comprising:
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sensing at least a part of a current passing through the diode and converting the sensed current to sensed voltage;
inputting the sensed voltage to a feedback amplifier for stabilizing the current passing through the diode; and
eliminating an offset voltage across inputs of the feedback amplifier by charging and discharging a first capacitor connected to one of the inputs of the feedback amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A pulse oximeter that converts pulses into light flashes, comprising:
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a diode for emitting the light flashes;
a feedback amplifier having inputs, a feedback capacitor, and an output, the feedback amplifier being operative to stabilize a current passing through the diode; and
a nulling amplifier having inputs, a nulling capacitor, and an output, the nulling amplifier being operative to charge and discharge the feedback capacitor until the inputs of the feedback amplifier are at a same voltage. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification