Passive pacer refractory circuit

Claim 1

In a pacer having a pair of ventricular electrodes, a timing capacitor, means for charging said capacitor, means responsive to the voltage across said capacitor reaching a predetermined value for discharging said capacitor and for supplying a stimulating pulse on said ventricular electrodes, means coupled to said ventricular electrodes for detecting and amplifying a heartbeat signal, said detecting and amplifying means including a transistor in the last stage thereof, transistor means for selectively discharging said timing capacitor, said last stage transistor and said discharging transistor means each having a base terminal and a collector terminal, means for capacitively coupling the collector terminal of said last stage transistor to said base terminal of said discharging transistor means for controlling the conduction thereof responsive to the detection of a heartbeat signal, the improvement comprising diode means connected between said timing capacitor and the collector terminal of said discharging transistor means poled in a direction to permit easy current flow from said timing capacitor to the collector terminal of said discharging transistor means, and regenerative resistive feedback means connected between the collector terminal of said discharging transistor means and the base terminal of said last stage transistor for controlling said last stage transistor and said discharging transistor to function as a one-shot multivibrator refractory circuit.