Frequency selective hysteresis comparator

A circuit, comprising:

• (a) hysteresis comparator means for wave shaping a pulse train signal wherein the hystersis loop transfer function of said comparator means has an input comparison region of a selected width whereby any signal driving said comparator and having a peak-to-peak amplitude less than said selected width of said input comparison region is not transmitted by said comparator, wherein said hysteresis comparator means comprises:
• (1) a high gain differential amplifier having inverting input means, non-inverting input means, and output means;
• (2) positive feedback resistor means coupled between said output means and said non-inverting input means;
• (3) input resistor means coupled between said non-inverting input means and said inverting input means;
• and
• (4) voltage divider means for providing a bias voltage to said inverting input means;
• (b) means for applying an input signal to said comparator;
• and
• (c) a differentiating network connected between said means for applying an input signal to said comparator and an input circuit for said comparator, wherein said differentiating network comprises:
• (1) a capacitor coupled in series between said means for applying an input signal and said input circuit for said comparator, wherein said capacitor has a capacitance selected to cause said input circuit to function as a passive element differentiating network, wherein a relatively low frequency component of said input signal is attenuated relative to a pulse train signal component of said input signal, and wherein said pulse train signal component has a selected repetition rate at least as great as the frequency of said relatively low frequency component.