Electronic function generator

Claim 1

ELECTRONIC FUNCTION GENERATING APPARATUS FOR PROVIDING AN OUTPUT POTENTIAL WHICH VARIES IN ACCORDANCE WITH THE LOGARITHMIC FUNCTION OF THE AMPLITUDE OF AN INDEPENDENT VARIABLE INPUT POTENTIAL WHICH IS DELIVERED FROM A SOURCE, COMPRISING IN COMBINATION, A PAIR OF DIODES CONNECTED IN A SERIES-OPPOSITION RELATIONSHIP BETWEEN THE SOURCE OF INPUT POTENTIAL AND AN OUTPUT TERMINAL, AND A REFERENCE VOLTAGE SOURCE INCLUDING A POSITIVE TEMPERATURE COEFFICIENT RESISTOR ELEMENT COUPLED TO THE COMMON JUNCTURE OF SAID PAIR OF DIODES AND BIASING ONE OF SAID PAIROF DIODES TO A CONDITION OF CONTINUOUS CONDUCTION WHEREBY, IN DEPENDENCE UPON THE AMPLITUDE OF THE INPUT SIGNAL THE OTHER OF SAID PAIR OF DIODES IS BIASED TO A CONDITION OF CONDUCTION, VARIATIONS IN THE AMPLITUDE OF THE INPUT POTENTIAL CAUSING CORRESPONDING VARIATIONS IN THE AMOUNT OF CURRENT WHICH IS CONDUCTED BY EACH OF SAID PAIR OF DIODES, AND A NEGATIVE COEFFICIENT RESISTOR ELEMENT CONNECTED IN SERIES CIRCUIT WITH SAID ONE OF SAID DIODES ON THE SIDE THEREOF REMOTE FROM COMMON JUNCTURE, SAID NEGATIVE TEMPERATURE COEFFICIENT RESISTOR HAVING A VLUE AND A COEFFCIENT TO PROVIDE WITH A CHANGE IN TEMPERATURE A CHANGE IN VOLTAGE DROP THERAACROSS SUBSTANTIALLY EQUAL TO THE DIFFERENCE BETWEEN THE CHANGES IN VOLTAGE DROPS ACROSS SAID FIRST AND SECOND DIODE ELEMENTS, WHEREBY VARIATION IN AMBIENT TEMPERATURE AFFECT ONLY THE AMPLITUDE OF POTENTIAL AT THE JUNCTION OF SAID PAIR OF DIODES TO MAINTAIN A CONTANT FLOW OF CURRENT THROUGH THE ONE OF SAID PAIR OF DIODES.