Circuit for removing unwanted slope transitions from an incoming signal

This invention provides a circuit for providing as an output voltage signal (S2) the differential of the voltage of an input signal (S1) on an input terminal, wherein the circuit includes an input capacitor (C1) for converting the input signal into a current proportional to the rate of change in the input signal, and the input signal includes an unwanted temporal portion, characterised by a circuit node (16) connected to the opposite side of said input capacitor from the input terminal and through at least one resistor (R2, R3) to the feedback resistor (R4) of an operational amplifier (U1-A); means (U1-B) for storing the voltage VH at this node on a holding capacitor (C5); means (200) responsive to said unwanted temporal portion of said signal for generating a reset signal; and means responsive to said reset signal and to the voltage on said holding capacitor for maintaining the voltage at said node at the voltage VH during said unwanted temporal portion of said signal.