Derivative circuit

Claim 1

A CIRCUIT FOR OBTAINING AS AN INPUT TO A HIGH INPUT IMPEDANCE DEVICE, THE FINITE DIFFERENCE APPROXIMATION TO THE DERIVATIVE OF A FUNCTION Y=F(X), IN WHICH F(X) REPRESENTS ANY INDEPENDENT VARIABLE, SAID FUNCTION BEING REPRESENTED BY AN ELECTRICAL SIGNAL WHOSE VOLTAGE, WITH RESPECT TO A REFERENCE POTENTIAL, VARIES IN ACCORDANCE WITH SAID FUNCTION, COMPRISING FIRST, SECOND AND THIRD NORMALLY OPEN GATES CONNECTED IN SERIES, SAID FIRST GATE HAVING AN INPUT FOR RECEIVING SAID ELECTRICAL SIGNAL AND SAID THIRD GATE HAVING AN OUTPUT; FIRST AND SECOND ANALOG VOLTAGE STORAGE ELEMENTS, SAID FIRST ELEMENT BEING CONNECTED BETWEEN SAID REFERENCE POTENTIAL AND THE JUNCTION OF SAID FIRST AND SECOND GATES, SAID SECOND ELEMENT BEING CONNECTED BETWEEN SAID REFERENCE POTENTIAL AND THE JUNCTION OF SAID SECOND AND THIRD GATES; A THIRD ANALOG VOLTAGE STORAGE ELEMENT; A FOURTH NORMALLY OPEN GATE, SAID THIRD STORAGE ELEMENT AND SAID FOURTH GATE BEING CONNECTED, IN THE ORDER STATED, BETWEEN SAID OUTPUT OF SAID THIRD GATE AND SAID REFERENCE POTENTIAL, THE INPUT OF THE HIGH INPUT IMPEDANCE DEVICE BEING CONNECTED TO THE JUNCTION OF SAID THIRD STORAGE DEVICE AND SAID FOURTH GATE; AN IMPEDANCE CONNECTED BETWEEN SAID OUTPUT OF SAID THIRD GATE AND SAID JUNCTION OF SAID FIRST AND SECOND GATES; AND MEANS CONNECTED TO SAID GATED FOR CLOSING SAID FIRST, THIRD AND FOURTH GATES AS A GROUP ALTERNATELY WITH SAID SECOND GATE.