Current amplifier providing selectable ratios of superimposed a.c. and d.c. outputs

Claim 1

A PLURAL-MODE CURRENT-AMPLIFIER CIRCUIT, COMPRISING FIRST AND SECOND CURRENT-AMPLIFYING STAGES CONNECTED IN CASCADE RELATIONSHIP, MEANS FOR APPLYING A SELECTABLE D.-C. VOLTAGE TO SAID FIRST STAGE TO PROVIDE A CONSTANT-CURRENT OUTPUT OF SELECTABLE AMPLITUDE THEREFROM, MEANS FOR CONNECTING A LOAD DEVICE IN THE OUTPUT CIRCUIT OF SAID SECOND STAGE, MEANS FOR APPLYING AN A.-C. VOLTAGE IN A.-C. SHUNT RELATIONSHIP WITH SAID APPLIED D.-C. VOLTAGE, THE PEAK AMPLITUDE OF SAID A.-C. VOLTAGE BEING A SELECTABLE PERCENTAGE OF SAID APPLIED D.-C. VOLTAGE, MEANS FOR CONCURRENTLY VARYING THE AMPLITUDES OF SAID A.-C. AND D.-C. VOLTAGES APPLIED TO SAID FIRST STAGE WHILE MAINTAINING CONSTANT SAID SELECTABLE PERCENTAGE RELATIONSHIP THEREBETWEEN TO PROVIDE A FIRST MODE OF OPERATION WHEREIN THE A.-C. COMPONENT OF CURRENT VARIATION IN THE OUTPUT CIRCUIT OF SAID SECOND STAGE IS A CONSTANT PERCENTAGE OF THE D.-C. COMPONENT THEREOF AS THE LATTER IS VARIED, MEANS FOR APPLYING A SECOND A.-C. VOLTAGE OF A SELECTABLE AMPLITUDE TO THE INPUT OF SAID SECOND STAGE IN THE ABSENCE OF SAID A.-C. INPUT TO SAID FIRST STAGE TO PROVIDE A SECOND MODE OF OPERATION WHEREIN THE A.-C. COMPONENT OF CURRENT VARIATION IN THE OUTPUT CIRCUIT OF SAID SECOND STAGE IS OF FIXED AMPLITUDE AND INDEPENDENT OF THE D.-C. COMPONENT THEREOF PROVIDED BY THE SELECTABLE LEVEL OF CONSTANT-CURRENT OUTPUT OF SAID FIRST STAGE.