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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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.
955 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