Demand cardiac pacemaker with input circuit portion of increased sensitivity
First Claim
1. A demand cardiac pacemaker circuit comprising:
- a. pulse generator means including timing circuit means operable for generating and applying output stimulator pulses at a selected frequency to the heart of the patient in which said demand pacemaker circuit is implanted; and
b. sensing circuit means responsive to a heart signal not always above a predetermined amplitude and comprising a first bipolar transistor of relatively high gain, unidirectional conducting means coupled to its base for maintaining the bias level of the base of said transistor, said unidirectional conducting means comprising a semiconductor device having a junction whose temperature dependent coefficients are coextensive with those of said first bipolar transistor, input means for applying the heart signal to said base of said first transistor, a second bipolar transistor of relatively high gain for further amplifying the output of said first transistor, and a feedback circuit including filter circuit means for applying the output of said second transistor to said first transistor, said filter circuit means for shaping the feedback signal to provide desired amplitude/frequency response characteristics of said sensing circuit means, whereby said sensing circuit is responsive to input signals of an amplitude above a predetermined level for generating and applying inhibit signals to said pulse generator means.
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Abstract
A demand cardiac pacemaker is disclosed as comprising an input sensing circuit portion of improved sensitivity to heart beat signals of relatively low amplitude. In particular, the input circuit portion includes a first sensing, bipolar transistor biased by a GaAsP light-emitting diode (LED), and a second amplifying, bipolar transistor whose base is coupled to the collector of the first transistor. Further, the output of the second transistor as taken from its collector is fed back through a suitable shaping circuit to the emitter of the first transistor, whereby controlled high gain and desired frequency/amplitude discrimination characteristics are achieved from the first and second transistors, so that the input sensing portion of the pacemaker circuit is responsive to heart signals above a predetermined level without sacrificing gain.
17 Citations
6 Claims
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1. A demand cardiac pacemaker circuit comprising:
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a. pulse generator means including timing circuit means operable for generating and applying output stimulator pulses at a selected frequency to the heart of the patient in which said demand pacemaker circuit is implanted; and b. sensing circuit means responsive to a heart signal not always above a predetermined amplitude and comprising a first bipolar transistor of relatively high gain, unidirectional conducting means coupled to its base for maintaining the bias level of the base of said transistor, said unidirectional conducting means comprising a semiconductor device having a junction whose temperature dependent coefficients are coextensive with those of said first bipolar transistor, input means for applying the heart signal to said base of said first transistor, a second bipolar transistor of relatively high gain for further amplifying the output of said first transistor, and a feedback circuit including filter circuit means for applying the output of said second transistor to said first transistor, said filter circuit means for shaping the feedback signal to provide desired amplitude/frequency response characteristics of said sensing circuit means, whereby said sensing circuit is responsive to input signals of an amplitude above a predetermined level for generating and applying inhibit signals to said pulse generator means. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification
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- Resources
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Current AssigneeMedtronic Incorporated (Medtronic Plc)
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Original AssigneeMedtronic Incorporated (Medtronic Plc)
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InventorsAlferness, Clifton
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Primary Examiner(s)Kamm, William E.
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Application NumberUS05/533,259Time in Patent Office743 DaysField of Search128/419 PG, 128/421, 128/422, 307/318, 307/302, 330/129, 330/138, 328/146, 328/148, 323/75 F, 323/222US Class Current607/9CPC Class CodesA61N 1/3704 Circuits specially adapted ...
