Differential threshold detector

Claim 1

An adaptive reference threshold detector for sensing a drop of predetermined magnitude in the level of an input signal from its peak value during an interval of time comprising: a voltage follower circuit including an operational amplifier having a positive input port coupled to said input signal and an output coupled through a diode to a capacitor, whereby said capacitor charges to the maximum voltage level at the output of said voltage follower circuit and thereby establishes a reference voltage derived from said input signal in cooperation with said voltage follower; an FET device having its gate coupled to said capacitor and its source coupled to the negative input port of said voltage follower circuit operational amplifier in a manner such that negative feedback is applied thereto; and a comparator circuit having a positive input port coupled to said input signal and a negative input port coupled to the source of said FET device through a resistive divider, thereby continuously comparing said input signal with said reference level and producing a logic level output signal whenever the difference in magnitude between said input signal and said reference level exceeds a preselected value.