Impedance bootstrap circuit for an interface of a monitoring device

Abstract

An interface for receiving electrical signals representative of a condition of a patient and for conveying representations of the electrical signals to a processing system. The interface includes at least one amplifier circuit configured to alter an amplitude of the electrical signal, a common-mode cancellation amplifier circuit coupled to the at least one amplifier circuit and configured to reduce common-mode signal noise in the electrical signals, and a bootstrap circuit coupled to the at least one amplifier circuit and configured to increase an effective input impedance at an input of the at least one amplifier circuit.

1 - 20 . (canceled) 
     
     
         21 . A system for monitoring a patient, the system comprising:
 a host computer;   a monitoring device for monitoring a level of consciousness of the patient, the monitoring device in communication with the host computer, the monitoring device including a control section having a plurality of keys configured to control functionality, a display connected to the control section and a plurality of physiological sensors configured for affixing to the patient's head to monitor brain activity of the patient, the plurality of physiological sensors measuring first bio-electric signals of the patient having a frequency band of two to four hundred eighty Hertz;   a high-frequency device for monitoring the patient applied to the patient, the high-frequency device in communication with the host computer, the high-frequency device configured for measuring second bio-electric signals of the patient; and   an instrumentation amplifier circuit configured to increase an amplitude of at least one of the first bio-electric signals and the second bio-electric signals.   
     
     
         22 . The device of  claim 21 , wherein the plurality of physiological sensors include three physiological sensors. 
     
     
         23 . The device of  claim 21 , wherein the plurality of physiological sensors include electrodes. 
     
     
         24 . The device of  claim 21 , wherein the bio-electric signals are comprised of electroencephalography signals. 
     
     
         25 . The device of  claim 21 , wherein the bio-electric signals are comprised of electrocardiography signals. 
     
     
         26 . The device of  claim 21 , wherein the monitoring device is in communication with the host computer through a universal host bus. 
     
     
         27 . The device of  claim 21 , wherein the monitoring device receives and processes bio-electric signals from the plurality of physiological sensors through a patient interface cable. 
     
     
         28 . The device of  claim 21 , further comprising:
 a common-mode cancellation amplifier circuit coupled to the instrumentation amplifier circuit and configured to reduce common-mode signal noise in at least one of the first bio-electric signals and the second bio-electric signals.   
     
     
         29 . The device of  claim 21 , further comprising:
 a bootstrap circuit coupled to the amplifier circuit and configured to increase an effective input impedance at an input of the instrumentation amplifier circuit.   
     
     
         30 . The device of  claim 21 , further comprising:
 an impedance check circuit coupled to the instrumentation amplifier circuit, the impedance check circuit configured to be coupled to a processing system of the monitoring device and enable automated checking of a physical interface between the physiological sensors and the patient and to receive impedance check signals from the processing system.   
     
     
         31 . The device of  claim 21 , wherein a path is defined between the plurality of physiological sensors and the instrumentation amplifier circuit and wherein the instrumentation amplifier circuit detects an error condition by monitoring impedance of said path.