Combined pacemaker delta modulator and bandpass filter

DETAILED DESCRIPTION It is a general object of my invention to provide a combined delta modulator and bandpass filter for a pacemaker sense circuit in which only a single amplifier is required.
The main advantage of the invention is not in the savings of components, although one less amplifier is required.
The main advantage of the invention is that an implanted pacemaker, or other device whose power consumption is to be minimized, would have one less amplifier which draws current, thus extending the life of the device.
In a typical delta modulator, the input signal is applied through the capacitor to the minus input of an operational (differential) amplifier, and a reference potential is applied to the plus input.
Depending on the polarity of the output of the operational amplifier during each sampling time, a current of one polarity or the other is caused to flow through the capacitor.
In accordance with the principles of my invention, a similar arrangement is employed.
However, instead of connecting the plus input of the amplifier to a reference potential, it is also coupled to the input signal.
Furthermore, the filter components are connected across both inputs of the amplifier.
It is not apparent from looking at the circuit why it functions as both a delta modulator and a bandpass filter.
That it does has to be demonstrated through mathematical analysis.