Circuit for measuring the dynamic impedance ratio of a nonlinear device

Claim 1

A CIRCUIT FOR DETERMINING THE RATIO OF THE DYNAMIC IMPEDANCE AT TWO POINTS IN THE OPERATING RANGE OF A DEVICE HAVING AN EXPONENTIALLY-VARYING VOLTAGE-CURRENT CHARACTERISTIC, THE CIRCUIT COMPRISING: A PAIR OF TERMINALS FOR EFFECTING AN ELECTRICAL CONNECTION WITH A DEVICE INSERTED INTO THE CIRCUIT, A CURRENT SOURCE FOR SUPPLYING A D.C. CURRENT AND A SUPERIMPOSED A.C. CURRENT TO SAID TERMINALS AND THE COMPONENT, THEREBY PRODUCING RESPECTIVE D.C. AND A.C. VOLTAGE ACROSS THE DEVICE, THE LEVEL OF THE D.C. CURRENT ESTABLISHING A FIRST POINT IN THE OPERATING RANGE OF THE DEVICE, MEANS COUPLED TO ONE OF SAID PAIR OF TERMINALS FOR PRODUCING A FIRST D.C. VOLTAGE EQUIVALENT TO THE A.C. VOLTAGE ACROSS THE DEVICE, MEANS COUPLED TO THE A.C. VOLTAGE PRODUCING MEANS FOR COMPARING THE LEVEL OF THE FIRST D.C. VOLTAGE TO A REFERENCE D.C. VOLTAGE LEVEL REPRESENTING THE DESIRED A.C. VOLTAGE ACROSS THE DEVICE AT THE FIRST POINT, THE COMPARING MEANS PROVIDING A DIFFERENCE VOLTAGE CORRESPONDING TO AN AMPLITUDE DIFFERENCE BETWEEN THE FIRST D.C. VOLTAGE AND THE REFERENCE VOLTAGE, VOLTAGE STORAGE MEANS SELECTIVELY CONNECTABLE TO SAID COMPARING MEANS FOR RECEIVING AND STORING THE DIFFERENCE VOLTAGE, MEANS COUPLED BETWEEN SAID VOLTAGE STORAGE MEANS AND SAID CURRENT SOURCE AND RESPONSIVE TO THE VOLTAGE STORED BY SAID VOLTAGE STORAGE MEANS FOR ADJUSTING THE AMPLITUDE OF THE A.C. CURRENT OUTPUT FROM SAID CURRENT SOURCE UNTIL THE LEVEL OF SAID FIRST D.C. VOLTAGE ADJUSTS TO SUBSTANTIALLY THE LEVEL OF SAID REFERENCE VOLTAGE, MEANS FOR DISCONNECTING SAID STORAGE MEANS FROM SAID COMPARING MEANS WHEREUPON THE AMPLITUDE RATIO OF THE A.C. TO THE D.C. CURRENT FROM SAID CURRENT SOURCE IS FIXED BY SAID STORAGE MEANS, MEANS FOR MULTIPLYING BOTH THE A.C. AND D.C. CURRENTS FROM SAID CURRENT SOURCE BY A PREDETERMINED FACTOR SO THAT THE LEVEL OF THE D.C. CURRENT ESTABLISHES A SECOND POINT IN THE OPERATING RANGE OF THE DEVICE, THE SUPERIMPOSED A.C. CURRENT THEREUPON PRODUCING A SECOND A.C. VOLTAGE ACROSS THE DEVICE, AND MEANS RESPONSIVE TO A CHANGE IN THE LEVEL OF THE ADJUSTED FIRST D.C. VOLTAGE CAUSED BY THE SECOND A.C. CURRENT, FOR INDICATING THE DYNAMIC IMPEDANCE RATIO OF THE DEVICE.