Resistor with high positive temperature coefficient

Claim 1

IN A RESISTOR HAVING A RESISTOR BODY WHICH HAS AT LEAST IN THE UPPER REGION OF THE OPERATING TEMPERATURE RANGE A POSITIVE TEMPERATURE COEFFICIENT OF THE RESISTANCE VALUE, SAID RESISTOR BODY BEING MADE OF FERROELECTRIC MATERIAL WITH A CURIE TEMPERATURE, ABOVE WHICH SUCH MATERIAL LOSES ITS PERMANENT POLARIZATION, LYING AT LEAST BELOW THE UPPER LIMIT OF THE OPERATING TEMPERATURE RANGE, SAID MATERIAL BEING CONDUCTIVE BY IMPURITY CENTERS INCLUDED THEREIN, WHEREBY THE RESPECTIVE SPACING OF THE DONORS FROM THE LINE BAND AND OF ACCEPTORS FROM THE VALENCE BAND IS CONSIDERABLY SMALLER THAN ONE HALF OF THE WIDTH OF THE PROHIBITED ZONE BETWEEN THE VALENCE BAND AND THE LINE BAND WHILE THE INTRINSIC CONDUCTIVITY OR CONDUCTIVITY DUE TO THE PRESENCE OF OTHER IMPURITY CENTERS IS LOWER AND ESPECIALLY NEGLIGIBLY LOW AS COMPARED WITH THE CONDUCTIVITY WHICH IS DUE TO THE PRESENCE OF SAID FIRST NAMED IMPURITY CENTERS; A DEVICE FOR ACHIEVING NEGLIGIBLY LOW VOLTAGE DEPENDENCE OF THE TOTAL RESISTANCE VALUE, SAID DEVICE COMPRISING CURRENT LEAD CONTACTS PLACED BARRIERFREE UPON SAID RESISTOR BODY AND BEING MADE OF A COMMON METAL SELECTED FROM THE CLASS OF METALS CONSISTING OF ALUMINUM AND ZINC OR OF AN ALLOY WITH A HIGH CONTENT OF AT LEAST ONE OF SAID COMMON METALS.