Transistor amplifier for controlling shaft speed

Claim 1

A CIRCUIT FOR CONTROLLING THE SPEED OF A ROTATING SHAFT BY SUPPLYING A CONTROLLED CURRENT TO A FIELD COIL THAT DICTATES THE SPEED OF THE SHAFT; WHICH CIRCUIT COMPRISES MEANS RESPONSIVE TO THE ROTATION OF THE SHAFT FOR PROVIDING A SIGNAL PROPORTIONAL TO THE SPEED THEREOF; A REFERENCE SIGNAL SOURCE FOR PRODUCING A SIGNAL CORRESPONDING TO THE DESIRED SPEED OF ROTATION OF SAID SHAFT; A FIRST TRANSISTOR COMPRISING A COLLECTOR, AN EMITTER AND A BASE; SAID RESPONSIVE MEANS AND SAID REFERENCE SIGNAL SOURCE BEING CONNECTED IN PARALLEL AND IN OPPOSED RELATION IN THE BASE-EMITTER PATH OF SAID FIRST TRANSISTOR; SAID RESPONSIVE MEANS AND SAID REFERENCE SIGNAL SOURCE EACH HAVING AN IMPEDANCE ELEMENT CONNECTED IN SERIES THEREWITH; THE IMPEDANCE OF EACH OF SAID IMPEDANCE ELEMENTS BEING SUBSTANTIALLY GREATER THAN THE IMPEDANCE OF THE BASE-EMITTER PATH OF SAID FIRST TRANSISTOR WHEN IN A CONDUCTIVE STATE; A SECOND TRANSISTOR HAVING AN EMITTER, A COLLECTOR AND A BASE; SAID COLLECTOR OF SAID SECOND TRANSISTOR BEING CONNECTED TO THE COLLECTOR OF SAID FIRST TRANSISTOR AND THE BASE OF SAID SECOND TRANSISTOR BEING CONNECTED IN THE EMITTER PATH OF SAID FIRST TRANSISTOR; A CONSTANT VOLTAGE DROP DIODE CONNECTED IN THE EMITTER PATH OF SAID SECOND TRANSISTOR; A SOURCE OF D.C. POTENTIAL HAVING A FIRST OUTPUT TERMINAL THEREOF CONNECTED IN THE EMITTER PATH OF SAID FIRST TRANSISTOR; A MAGNETIC AMPLIFIER HAVING A PAIR OF INPUT AND OUTPUT TERMINALS; ONE OF SAID INPUT TERMINALS OF SAID MAGNETIC AMPLIFIER BEING CONNECTED TO THE COLLECTOR OF SAID FIRST TRANSISTOR AND TO THE COLLECTOR OF SAID SECOND TRANSISTOR; THE OTHER OF SAID INPUT TERMINALS OF SAID MAGNETIC AMPLIFIER BEING CONNECTED TO A SECOND OUTPUT TERMINAL OF SAID SOURCE OF POTENTIAL; THE OUTPUT TERMINALS OF SAID MAGNETIC AMPLIFIER BEING CONNECTED TO THE FIELD COIL; AND SAID CONSTANT VOLTAGE DROP DIODE BEING CONNECTED TO THE FIRST OUTPUT TERMINAL OF SAID SOURCE OF POTENTIAL SO THAT A CONSTANT VOLTAGE DROP IS MAINTAINED ACROSS SAID DIODE.