High input impedance direct-coupled transistor amplifier including negative-feedback means

Claim 1

A TRANSISTOR-TYPE A.C. AMPLIFIER HAVING AT LEAST TWO STAGES AND SUPPLIED FROM A D.C. SOURCE HAVING GROUNDED AND UNGROUNDED TERMINALS OF OPPOSITE POLARITY CHARACTERIZED IN THAT THE TRANSISTORS OF SUCCESSIVE STAGES ARE CONDUCTIVELY COUPLED IN EMITTER-TO-BASE CONFIGURATION WITH THE EMITTERS OF ALL TRANSISTORS EXCEPT THAT OF THE FINAL STAGE HAVING NO D.C. CONNECTION TO SAID GROUNDED TERMINAL; THE EMITTER OF THE FINAL-STAGE TRANSISTOR IS CONNECTED TO SAID GROUNDED TERMINAL SLOELY BY AN UNBYPASSED FIRST RESISTANCE MEANS WHICH IS TRAVERSED BY THE TOTAL D.C. EMITTER CURRENT OF ALL STAGES AND IS COMMON TO THE A.C. INPUT AND A.C OUTPUT CIRCUITS OF THE AMPLIFIER; THE COLLECTOR OF EACH TRANSISTOR EXCEPT THAT OF THE FINAL STAGE IS CONNECTED TO A POINT OF FIXED D.C. REFERENCE POTENTIAL WITH RESPECT TO SAID GROUNDED TERMINAL; THE COLLECTOR OF THE FINAL-STAGE TRANSISTOR IS CONNECTED TO SAID UNGROUNDED TERMINAL OF THE D.C. SOURCE BY A SECOND RESISTANCE MEANS AND TO THE BASE OF THE INPUTSTAGE TRANSITOR BY THIRD RESISTANCE MANS OF A FEEDBACK CIRCUIT; FOR TEMPERATURE-STABILIZATION OF THE D.C. OPERATING POINTS OF ALL TRANSISTORS AND HIGH INPUT-IMPEDANCE OF THE AMPLIFIER, (A) THE RESISTANCE VALUE OF SAID SECOND RESISTANCE MEANS IS OF THE SAME OF HIGH ORDER RELATIVE TO SAID FIRST RESISTANCE MEANS, AND (B) THE RESISTANCE VALUE OF SAID THIRD TRANSISTANCE MEANS IS OF THE ORDER OF MEGOHMS AND GREAT RELATIVE TO THE RESISTANCE VALUES OF SAID FIRST ANS SECOND RESISTANCE MEANS.