Abstract: A device such as a cardiac pacemaker or other implantable biomedical device, and method of operation thereof, containing one or more switchable circuits. A control system, preferably incorporating a microprocessor, controls predetermined changes of the operating characteristics of the switchable circuits. In a cardiac pacer embodiment, a circuit such as the input amplifier can be switched to have different characteristics, e.g. filter setting and sensitivity, during predetermined portions of the pacer cycle. Further, the operation of a circuit can be monitored over a plurality of operating cycles, with controlled switching of the circuit characteristics as a function of cumulative monitored circuit performance. A specific example of the invention is shown for changing characteristics of a filter circuit used in a pacer which adjusts the pacer rate as a function of determined stimulus-T wave time interval.

Abstract: A self-adjusting voltage regulator circuit on a CMOS chip, for use with CMOS digital and/or analog circuit, providing a voltage which is selected in accordance with the characteristics of the chip to optimally current control operation of CMOS circuits on this chip. The voltage regulator circuit has a reference CMOS pair with a predetermined geometry, and current means are provided for driving a current through said reference pair which is adjusted to operate the pair at a desired point of current controlled operation. The voltage across the reference pair is utilized to provide the regulated voltage to other CMOS pairs, which pairs have respective geometries of predetermined relation to the reference pair geometry, whereby the regulated voltage and the relative geometry provide current controlled operation of each such CMOS pair.

Abstract: A physiological stimulating system includes improved means for minimizing the polarization that results at the stimulus site, thereby enabling enhanced detection of evoked responses. In the pacemaker embodiment, the stimulus signal comprises positive recharge pulses immediately before and immediately after the negative stimulus signal, the recharge pulses being adapted in a time duration and amplitude such that the total current delivered to the stimulus site, (e.g., a patient's heart) by the stimulus signal is substantially zero.

Abstract: A physiological stimulating system includes improved means for minimizing the polarization that results at the stimulus site, thereby enabling enhanced detection of evoked responses. In the pacemaker embodiment, the stimulus signal comprises positive recharge pulses immediately before and immediately after the negative stimulus signal, the recharge pulses being adapted in a time duration and amplitude such that the total current delivered to the stimulus site, (e.g., a patient's heart) by the stimulus signal is substantially zero.

Abstract: An improved automatically rate adaptive pacemaker, wherein the rate of delivered stimulus pulses is controlled as a function of sensed hearbeat characteristics and/or patient threshold. The pacemaker analyzes different characteristics or parameters of the detected heartbeat signal, and the rate of delivered stimulus pulses is controlled as a function of predetermined correlation factors. The pacemaker includes means for automatic threshold tracking, and also for adjusting the rate of delivered stimulus pulses as a continuous function of the patient threshold.

Abstract: A monolithic pacer is provided which utilizes I.sup.2 L circuitry in combination with linear transistors, providing the conventional advantages of analog circuitry together with the flexibility of digital circuitry. Low current drain operation is achieved by current source control of circuit operating conditions, with I.sup.2 L gates being utilized alone and in combination with linear transistors to provide current sources. The pacer provides "on-demand" logic and is externally programmable.