| 摘要 |
<p>A cardiac pacemaker (10) has a sense amplifier (20) responsive to signals representative of cardiac activity for passing signal components lying in a selectively variable pass band and for selectively varying the gain of the passed signal. A pair of signal comparators (58, 59) constituting switched capacitor amplifiers, associated with the sense amplifier (20), are responsive to the filtered and gain adjusted signal for comparison of its magnitude to predetermined target levels for determination of heart rate and the need for change of rate. Two target levels are provided in each comparator (58, 59) for comparison with the level of the detected signal, by multiplexing the switched capacitors. Another switched capacitor amplifier (99) is used to develop a voltage reference level insensitive to temperature, supply voltage, and circuit components, for deriving the target levels for the comparison. Still another multiplexed switched capacitor amplifier comparator (125) is used to develop a first target level to regulate the level of the pacing stimulus, and a second target level for comparison with the supply voltage level of the pacemaker as a measure of the point at which the pacemaker requires replacement.</p> |
