Direct coupled amplifier for amplifying low level information signals and rejecting interference signals

Claim 1

IN A DIRECT COUPLED AMPLIFIER HAVING A DIFFERENTIAL FIRST STAGE INCLUDING A PAIR OF TRANSISTORS EACH HAVING AN EMITTER, A BASE AND A COLLECTOR, AN INTERFERENCE SIGNAL REJECTOR CIRCUIT INCLUDING AMPLIFIER MEANS HAVING FIRST AND SECOND INPUT TERMINALS AND FIRST AND SECOND OUTPUT TERMINALS; A SOURCE OF POTENTIAL; MEANS CONNECTING SAID SOURCE OF POTENTIAL TO SAID FIRST INPUT TERMINAL OF SAID AMPLIFIER; MEANS FOR DETECTING CHANGE IN THE SUM OF THE CURRENTS FLOWING THROUGH SAID TRANSISTORS CONNECTED TO SAID SECOND INPUT TERMINAL OF SAID AMPLIFIER THEREBY TO APPLYING A POTENTIAL INDICATIVE OF SAID SUM OF CURRENTS TO SAID SECOND INPUT TERMINAL; AND FEEDBACK MEANS CONNECTED BETWEEN SAID FIRST OUTPUT TERMINAL OF SAID AMPLIFIER MEANS AND SAID FIRST STAGE;