Cardiac pacemaker with operational amplifier output circuit

A medical electrical stimulator apparatus, comprising:

• a timing circuit for triggering the generation of stimulation pulses;
• and
• a pulse generator triggered by said timing circuit to generate stimulation pulses, said pulse generator comprising an operational amplifier having an amplifier output and having first and second amplifier inputs;
• a first electrode electrically coupled to said first input of said amplifier;
• a virtual load electrically coupled between said first electrode and said first input of said amplifier;
• second input of said amplifier;
• and
• voltage source means for providing defined pulsatile voltage waveforms to said second input of said amplifier to cause corresponding delivery of voltage pulses to said first electrode.

A cardiac pacer apparatus, comprising:

• a resettable timing circuit for triggering the generation of stimulation pulses;
• a pulse generator triggered by said timing circuit to generate stimulation pulses, said pulse generator comprising an operational amplifier having an amplifier output for providing electrical signals and having first and second amplifier inputs;
• a first electrode electrically coupled to said first input of said amplifier;
• a virtual load electrically coupled between said first electrode and said first input of said amplifier;
• a second electrode electrically coupled to said second input of said amplifier;
• and
• voltage means for providing defined pulsatile voltage waveforms to said second input of said amplifier to cause corresponding delivery of voltage pulses to said first electrode;
• and
• means for detecting a heart depolarization and for resetting said timing circuit in response to detection of a said depolarization, said detecting means responsive to electrical signals provided by said output of said operational amplifier.

Apparatus for detecting and stimulating depolarization of cardiac tissue, comprising:

• an active circuit having first and second inputs and an output and having means for maintaining said first and second inputs at the same voltage;
• a first electrode;
• a virtual load coupled between said first electrode and said first input;
• a second electrode coupled to said second input;
• and
• voltage source means for providing pulsatile voltage signals having defined waveforms to said second input;
• wherein said maintaining means comprises means for maintaining said first and second inputs at the same voltage by delivering electrical energy through said virtual load and said first electrode and wherein said output of said active circuit provides a signal indicative of the electrical energy delivered through said virtual load.

Apparatus for stimulating tissue, comprising:

• an active circuit having first and second inputs and an output and having means for maintaining said first and second inputs at the same voltage;
• a first electrode;
• a virtual load coupled between said first electrode and said first input;
• a second electrode coupled to said second input;
• and
• voltage source means for providing pulsatile voltage signals having defined waveforms to said second input;
• wherein said maintaining means comprises means for maintaining said first and second inputs at the same voltage by delivering electrical energy through said virtual load and said first electrode, whereby a voltage pulse is delivered to said first electrode in response to the provision of a pulsatile voltage signal by said voltage source means.