Abstract: One embodiment is directed to a sensor for measuring a skeletal system. A signal path of the system comprises an amplifier (612), a sensor element, and an amplifier (620). The sensor element comprises a transducer (4), a waveguide (5), and a transducer (30). An external condition is applied to the sensor element. For example, the sensor element is placed in an artificial orthopedic joint to measure loading of the joint. Pulsed energy waves are emitted by the transducer (4) into the waveguide (5). The transducer (30) receives each pulsed energy wave after it propagates through the waveguide (5). The transit time of each pulsed energy wave corresponds to the external condition applied to the sensor. The transducer (30) outputs a signal corresponding to each pulsed energy wave. A detection circuit edge detects the signal and outputs a pulse to the transducer (4) to generate a new pulse energy wave.

Abstract: At least one embodiment is directed to a sensor for measuring a skeletal system. A signal path of the system comprises an amplifier (612), a sensor element, and an amplifier (620). The sensor element comprises a transducer (4), a waveguide (5), and a reflecting surface (30). An external condition is applied to the sensor element. For example, the sensor element is placed in an artificial orthopedic joint to measure loading of the joint. Pulsed energy waves are emitted by the transducer (4) into the waveguide (5) and the reflected back to be received by the transducer (4). The transit time of each pulsed energy wave corresponds to the external condition applied to the sensor. The transducer (4) outputs a signal corresponding to each pulsed energy wave. A detection circuit edge detects the signal and outputs a pulse to the transducer (4) to generate a new pulse energy wave.

Abstract: At least one embodiment is directed to a sensor for measuring a parameter. A signal path of the system comprises an amplifier (612), a sensor element, and an amplifier (620). The sensor element comprises a transducer (4) at a first location of a waveguide (5), and a reflective surface (30) at a second location of the waveguide (5). A parameter such as force or pressure applied to the sensor element can change the length of waveguide (5). A pulsed energy wave is emitted by the transducer (4) into the waveguide (5) at the first location. The transducer (4) is responsive to pulsed energy waves reflected from reflective surface (30) to the second location. The transit time of each pulsed energy wave is measured. The transit time corresponds to the pressure or force applied to the sensor element.

Abstract: Apparatus and method provide flexibility in generating a stimulation waveform to an electrode of an implantable medical device. The stimulation waveform comprises at least one stimulation pulse. The embodiment of the invention supports a generation of a stimulation pulse in which an amplitude and an electrical polarity of the stimulation pulse can be dynamically changed. The embodiment comprises a capacitor arrangement, a regulator and a switching array. The capacitor arrangement can be reconfigured with respect to an electrical reference through the switching array in order for the regulator to deliver the stimulation pulse to a pair of electrodes. In another embodiment, a plurality of stimulation waveforms are generated in which different stimulation waveforms are associated with different electrodes. With the embodiment, a plurality of regulators are connected and reconfigured to the capacitor arrangement in order that the different stimulation waveforms are generated by different regulators.

Abstract: Disclosed are techniques for operation of neurostimulation or drug delivery devices to stop treatment therapy during times when the patient does not need to be treated. Advantageously, the present invention reduces battery usage and/or drug dosage during periods when treatment therapy need not be provided. Further, the present invention slows or reduces the tolerance the patient may develop from the electrical stimulation or treatment therapy. In one embodiment, the present invention includes a timer or a real time clock for shutting off the device during periods when the patient is sleeping in accordance with a preset schedule. The present invention preferably turns off after the patient has fallen asleep and right before the patient has awakened. Alternatively, the invention may include a sensor for sensing conditions indicative of whether the patient is awake or asleep. This sensed information may also be used to determine whether the treatment therapy should be delivered or stopped.

Abstract: The present invention discloses techniques for operation of neurostimulation or drug delivery devices to stop treatment therapy during times when the patient does not need to be treated. Advantageously, the present invention reduces battery usage and/or drug dosage during periods when treatment therapy need not be provided. Further, the present invention slows or reduces the tolerance the patient may develop from the electrical stimulation or treatment therapy. In one embodiment, the present invention includes a timer or a real time clock for shutting off the device during periods when the patient is sleeping in accordance with a preset schedule. The present invention preferably turns off after the patient has fallen asleep and right before the patient has awakened. Alternatively, the invention may include a sensor for sensing conditions indicative of whether the patient is awake or asleep. This sensed information may also be used to determine whether the treatment therapy should be delivered or stopped.

Abstract: A current limiting apparatus that is adapted to be operatively connected as part of a conductive loop formed by a medical device implanted within a living organism having electrically excitable tissue. This apparatus limits unwanted current in the conductive loop that may be induced by a significant level of an external signal such as a time-alternating electromagnetic field. This apparatus includes a switch for introducing a high impedance into the conductive loop when the switch is turned off. The apparatus also includes a control circuit that controls the switch to be turned on when the conductive loop should be closed to stimulate the electrically excitable tissue for a therapeutic effect. The control circuit turns the switch off whenever the living organism enters an area having a significant level of external signal that may induce unwanted current in the conductive loop to limit the unwanted current.

Abstract: A current limiting apparatus that is adapted to be operatively connected as part of a conductive loop formed by a medical device implanted within a living organism having electrically excitable tissue. This apparatus limits unwanted current in the conductive loop that may be induced by a significant level of an external signal such as a time-alternating electromagnetic field. This apparatus includes a switch for introducing a high impedance into the conductive loop when the switch is turned off. The apparatus also includes a control circuit that controls the switch to be turned on when the conductive loop should be closed to stimulate the electrically excitable tissue for a therapeutic effect. The control circuit turns the switch off whenever the living organism enters an area having a significant level of external signal that may induce unwanted current in the conductive loop to limit the unwanted current.

Abstract: Undesirable cross-conduction between electrode pairs in a human-implantable dual channel neurostimulator is prevented. The first and second pairs of electrodes may, optionally, share a common electrode. The first electrode pair is stimulated and then recharged. Then, after a finite waiting period has elapsed, the second electrode pair is stimulated and then recharged. Then, after a finite waiting period, the process is repeated. A high impedance state is established across one of the electrode pairs while the other electrode pair is being stimulated and recharged. Such a high impedance state prevents current from flowing through one of the electrode pairs while the other electrode pair is being stimulated or recharged.

Abstract: A first electrical signal and a second electrical signal are transmitted to one or more implanted leads including first and second electrodes, respectively. The first and second signals have a difference in frequency such that the combined potentials induce action potentials in a certain locus of electrically excitable tissue. Means are provided for adjusting the frequency difference, as well as the amplitudes of the signals so that the locus is altered.

Abstract: A new and improved all monolithic transceiver manufactured on a single semiconductor die and operative from a 5 volt DC power supply. The transceiver meets all of the pulse width and timing requirements of the MIL-STD-1553 transceiver and is operative at high switching speeds and high output current levels to generate bi-phase TX OUT and TX OUT signals used to drive, respectively, two center tapped primary windings of an output transformer. The transmitter includes two dynamically driven data channels which are driven out of phase and in a controlled manner that ensures that one data channel has been completely turned off before the other data channel turns on, thereby maximizing power transfer and operating efficiency while minimizing unnecessary current drain and eliminating current spiking in the output of the transmitter.

Abstract: A body implantable stimulator having an output capacitance that is periodically charged to a predetermined energy level and discharged through an electrode coupled to body tissue. The discharge pulse width is controlled by a semiconductor switch and after a short delay the capacitor is recharged rapidly to its original charge. The recharge current is regulated by a differential circuit responsive to the voltage on a reference capacitor and the output capacitor, both capacitors being coupled to the active electrode.

Abstract: A sample and hold circuit for producing an output voltage the magnitude of which is representative of the peak magnitude of a sampled input signal. The sample and hold circuit comprises a unity gain amplifier having an input terminal to receive said input signal and a cascoded output section for sourcing current at an output terminal. A discharge circuit is provided which includes a cascoded section for sinking current at said output terminal. Each of said cascoded sections being coupled to a capacitive load for charging or discharging the capacitor respectively to provide said output voltage.

Abstract: A demand cardiac pacemaker of the type having sense amplifier circuitry for detecting the occurrence of natural heart activity which establishes a first level representative of sensed extraneous repetitive noise and a second level greater in absolute value than the reference by an amount representative of sensed heart activity. Circuitry differentially responsive to the difference between the reference and second level detects the occurrence of natural heart activity. The sense amplifier circuitry is blanked, that is disconnected from the terminals coupled to the heart, for a blanking interval following stimulation to avoid saturation of the sense amplifier stages and the erroneous detection of a pacing stimulus. Any reference level voltages developed by extraneous repetitive noise are retained during blanking to prevent the differential circuitry from interpreting the noise signal sensed at the end of the blanking interval as a heart signal.

Abstract: A cardiac pacemaker of the type responsive to heart activity to affect the operation of the pacemaker. Detecting circuitry is provided having a differential input and an essentially polarity independent degree of response to sensed signals. A single polarity output signal is provided representative of sensed signals of either polarity. In a preferred embodiment, a differential input and differential output preamplifier is responsive to sensed signals to provide output signals of opposite polarity but like absolute value. An absolute value circuit responds to the opposite polarity signals to provide a single polarity output signal, the output signal being the same polarity without regard to the polarity of the sensed signals.

Abstract: A body implantable stimulator for providing stimulation signals having selectable energy levels. The stimulator provides a series of one of a predetermined plurality of independent output initiate signals and responds to those signals to provide stimulation signals having an amplitude, duration and repetition rate established by the series of output initiate signals that is provided.

Abstract: A cardiac pacemaker of the type responsive to a natural heart activity for affecting the operation of the pacemaker. Circuitry is provided which has an essentially polarity independent degree of response to sensed signals. In a preferred embodiment, the circuitry includes a differential input and a differential output, the output signals being of opposite polarity but of the same absolute value and being representative of sensed signals.

Abstract: A cardiac pacemaker of the type responsive to heart activity to affect the operation of the pacemaker. Detecting circuitry detects the presence of signals representative of natural heart activity. In a preferred embodiment, bias circuitry establishes the sensitivity of the detecting circuit, the sensitivity being altered during the provision of an output signal to enhance the response of the detecting circuit to the natural heart activity representative signals. In essence, hysteresis is provided in that the sensitivity of the detecting circuit is increased during initiation of the output signal and reduced during termination of that signal.

Abstract: A monolithic integrated comparator amplifier is provided for comparing an input signal to a nominal reference voltage to produce an output signal only when the input signal is less than the magnitude of the nominal reference voltage. Bidirectional hysteresis is introduced into the amplifier circuit by reducing the magnitude of the nominal reference voltage when the magnitude of the input signal becomes substantially equal to or greater than the nominal reference voltage produced when the amplifier is in a nominal operating state. The magnitude of the reference voltage is controlled by using a feedback switching transistor to vary the resistance of a resistive divider to decrease the reference voltage produced thereby.

Abstract: One shot and doubling one shot circuits are disclosed which produce fixed width output pulses in response to alternating input signals being applied thereto. Integrated injection logic (I.sup.2 L) and linear integrated circuit techniques are combined in the fabrication of the two circuits. Both the one shot and doubling one shot circuit comprises a switching transistor which is rendered conductive and nonconductive to produce the output pulse at its collector electrode. In response to the positive going transition of the input signal triggering signals are generated to render the switching transistor conductive. Conjointly, a capacitor is caused to charge toward a fixed potential until the magnitude of the voltage thereacross reaches a predetermined value which trips an output of a comparator circuit. The tripping of the comparator causes the switching transistor to be rendered nonconductive until the next positive going transition of the input signal.