Virtual right leg drive and augmented right leg drive circuits for common mode voltage reduction in ECG and EEG measurements
First Claim
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1. An isolated amplifier for use in a system having an earth ground comprising:
- a main amplifier having first and second inputs for receiving signals, said main amplifier including means for receiving at least one power supply voltage and having a circuit ground electrically isolated from said earth ground;
means for sensing a common mode voltage received by said first and second inputs and having an output for providing a compensation voltage representative of said common mode voltage; and
a capacitance to said earth ground for receiving said compensation voltage, said means for sensing and said capacitance causing said at least one power supply voltage to track said common mode voltage.
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Abstract
An isolated amplifier, typically a biomedical amplifier, includes a main amplifier having inputs for receiving signals, a circuit for sensing a common mode voltage received by the inputs from the electrodes and providing a compensation voltage representative of the common mode voltage, and a capacitance to chassis ground for receiving a voltage representative of the compensation voltage. The circuit and the capacitance cause the amplifier power supply voltages to track the common mode voltage. The capacitance permits the feedback loop gain to be increased, thereby reducing common mode voltage errors.
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Citations
20 Claims
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1. An isolated amplifier for use in a system having an earth ground comprising:
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a main amplifier having first and second inputs for receiving signals, said main amplifier including means for receiving at least one power supply voltage and having a circuit ground electrically isolated from said earth ground; means for sensing a common mode voltage received by said first and second inputs and having an output for providing a compensation voltage representative of said common mode voltage; and a capacitance to said earth ground for receiving said compensation voltage, said means for sensing and said capacitance causing said at least one power supply voltage to track said common mode voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An isolated amplifier for use in a system having an earth ground comprising:
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a main amplifier having first and second inputs for receiving signals, said main amplifier having a circuit ground electrically isolated from said earth ground; a circuit for sensing a common mode voltage received by said first and second inputs and having an output for providing a compensation voltage representative of said common mode voltage; an augmentation capacitance connected to said earth ground; means responsive to the compensation voltage provided by said circuit for coupling a first voltage representative of said compensation voltage to a patient and for coupling a second voltage representative of said compensation voltage to said capacitance, said second voltage being larger than said first voltage. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A biomedical amplifier for use in a system having an earth ground comprising:
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a main amplifier having first and second inputs for receiving signals, said main amplifier including means for receiving at least one power supply voltage and having a circuit ground electrically isolated from said earth ground; means for sensing a common mode voltage received by said first and second inputs and providing a compensation voltage representative of said common mode voltage; and a capacitance to said earth ground for receiving said compensation voltage, said means for sensing and said capacitance causing said at least one power supply voltage to track said common mode voltage. - View Dependent Claims (19, 20)
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Specification