Power amplifier

Claim 1

A POWER AMPLIFIER COMPRISING, AN INPUT STAGE FOR RECEIVING AT ITS INPUT SIGNALS TO BE AMPLIFIED, A POWER OUTPUT STAGE HAVING AN INPUT COUPLED TO THE OUTPUT OF SAID INPUT STAGE AND HAVING AN OUTPUT FURNISHING THE SIGNAL OUTPUT OF SAID AMPLIFIER, A NEGATIVE FEEDBACK PATH COUPLING SAID OUTPUT OF SAID POWER OUTPUT STAGE TO SAID INPUT OF SAID INPUT STAGE, SAID INPUT STAGE COMPRISING, AN ELECTRON TUBE HAVING AT LEAST A PLATE, CATHODE AND CONTROL GRID, THE SHUNT COMBINATION OF AN INDUCTOR, CATHODE CAPACITOR AND CATHODE RESISTOR IN SERIES WITH SAID CATHODE, A LOAD RESISTOR IN SERIES WITH AND COUPLING SAID PLATE TO A POTENTIAL SOURCE, MEANS FOR APPLYING SAID INPUT SIGNALS TO THE GRID OF SAID ELECTRON TUBE, MEANS FOR DERIVING OUTPUT SIGNALS FROM THE PLATE OF SAID ELECTRON TUBE FOR APPLICATION TO SAID INPUT OF SAID POWER OUTPUT STAGE, SAID INPUT STAGE BEING LOADED BY OUTPUT CAPACITY AND THE INPUT RESISTANCE OF THE FOLLOWING STAGE, MEANS FOR PROVIDING SAID INPUT STAGE WITH A SUBSTANTIALLY FLAT FREQUENCY RESPONSE BELOW A FIRST FREQUENCY, A DECREASING FREQUENCY RESPONSE FROM SAID FIRST FREQUENCY TO A SECOND HIGHER FREQUENCY, A SUBSTANTIALLY FLAT FREQUENCY RESPONSE FROM SAID SECOND FREQUENCY TO A CUTOFF FREQUENCY, AND A DECREASING FREQUENCY RESPONSE ABOVE SAID CUTOFF FREQUENCY, SAID LAST MENTIONED MEANS BEING PROVIDED BY ARRANGING SAID INPUT STAGE WHEREBY SAID CUTOFF FREQUENCY IS THE RECIPROCAL OF THE PRODUCT OF SAID OUTPUT CAPACITY WITH THE PARALLEL RESISTANCE COMBINATION OF SAID LOAD RESISTOR, SAID INPUT RESISTANCE AND THE PLATE RESISTANCE OF SAID ELECTRON TUBE, WHEREBY THE PRODUCT OF THE AMPLIFICATION FACTOR OF SAID ELECTRON TUBE WITH THE IMPEDANCE OF SAID INDUCTOR AT SAID FIRST FREQUENCY IS APPROXIMATELY EQUAL TO THE SUM OF SAID LOAD RESISTANCE AND SAID PLATE RESISTANCE, WHEREBY SAID CATHODE RESISTANCE IS SUBSTANTIALLY EQUAL TO THE IMPEDANCE OF SAID INDUCTOR AT SAID SECOND FREQUENCY, AND FURTHER WHEREBY THE PRODUCT OF SAID CATHODE CAPACITOR WITH SAID CATHODE RESISTOR IS SUBSTANTIALLY EQUAL TO THE PRODUCT OF SAID OUTPUT CAPACITY WITH THE RESISTANCE OF SAID PARALLEL RESISTANCE COMINATION.