Differential amplifier

Claim 1

A DIFFERENTIAL AMPLIFIER PROVIDING A FIRST OUTPUT SIGNAL PROPORTIONAL TO THE DIFFERENCE BETWEEN A PAIR OF INPUT SIGNALS AND A SECOND OUTPUT SIGNAL WHICH IS THE NEGATIVE COUNTERPART OF THE FIRST OUTPUT SIGNAL COMPRISING, IN COMBINATION: A FIRST AMPLIFIER STAGE HAVING A PAIR OF INPUT TERMINALS, ONE BEING CONNECTED TO GROUND POTENTIAL, SAID FIRST AMPLIFIER STAGE INCLUDING AN ELECTRONIC AMPLIFIER TUBE HAVING AT LEAST A CATHODE, AN ANODE AND A CONTROL GRID, THE OTHER OF SAID INPUT TERMINALS BEING CONNECTED TO SAID CONTROL GRID, AND THE AMPLIFICATION FACTOR OF SAID TUBE BEING MUCH GREATER THAN UNITY, A PAIR OF TERMINALS FOR A POWER SUPPLY FOR SAID ELECTRONIC TUBE, ONE OF SAID TERMINALS BEING CONNECTED TO GROUND POTENTIAL, A LOAD RESISTANCE CONNECTED BETWEEN SAID ANODE AND THE OTHER OF SAID POWER SUPPLY TERMINALS, A SECOND AND A THIRD RESISTANCE CONNECTED IN SERIES BETWEEN SAID CATHODE AND SAID ONE INPUT TERMINAL, SAID SECOND RESISTANCE BEING CONNECTED TO SAID CATHODE AND HAVING A NUMERICAL VALUE WHICH IS MUCH GREATER THAN THE RECIPROCAL OF THE MUTUAL TRANSCONDUCTANCE OF THE TUBE TO WHICH IT IS CONNECTED, AND AN OUTPUT TERMINAL CONNECTED TO THE JUNCTION BETWEEN SAID SECOND AND THIRD RESISTANCES, SAID GROUNDED INPUT TERMINAL CONSTITUTING ANOTHER OUTPUT TERMINAL; A SECOND AMPLIFIER STAGE COMPRISING A SYMMETRICAL DUPLICATE OF SAID FIRST AMPLIFIER STAGE; A FIRST CAPACITANCE CONNECTED BETWEEN THE ANODE END OF SAID LOAD RESISTANCE OF SAID FIRST STAGE AND THE JUNCTION BETWEEN THE CATHODE RESISTANCES OF SAID SECOND STAGE; AND A SECOND CAPACITANCE CONNECTED SIMILARLY BETWEEN THE LOAD RESISTANCE OF THE SECOND STAGE AND THE JUNCTION BETWEEN THE CATHODE RESISTANCES OF THE FIRST STAGE, SAID FIRST AND SECOND CAPACITANCES BEING OF SUCH VALUE AS TO CONSTITUTE A VIRTUAL SHORT CIRCUIT TO A.C. FREQUENCIES DOWN TO THE LOWEST A.C. FREQUENCY WHICH IT IS DESIRED TO INCLUDE IN THE FREQUENCY RANGE OF THE DIFFERENTIAL AMPLIFIER.