Suppression of grid current effects in d. c. amplifiers

Claim 1

A STABILIZED D.C. AMPLIFIER SYSTEM COMPRISING IN COMBINATION: A SIGNAL INPUT TERMINAL; AN OUTPUT TERMINAL; A COMMON TERMINAL; A MULTI-STAGE D.C. AMPLIFIER HAVING AN INPUT STAGE COUPLED BETWEEN SAID INPUT AND COMMON TERMINALS, AND HAVING AN OUTPUT STAGE COUPLED BETWEEN SAID OUTPUT AND COMMON TERMINALS, EACH STAGE HAVING A PLURALITY OF ELECTRODES INCLUDING AT LEAST ONE GRID; A FEEDBACK CIRCUIT CONNECTED BETWEEN SAID OUTPUT TERMINAL AND SAID INPUT TERMINAL; AN INPUT CAPACITOR CONNECTED BETWEEN SAID INPUT TERMINAL AND THE GRID OF SAID INPUT STAGE SO AS TO BLOCK THE FLOW OF GRID CURRENT FROM THE SAID LASTNAMED GRID TO SAID INPUT TERMINAL; A BALANCING AMPLIFIER COUPLED BETWEEN SAID INPUT TERMINAL AND SAID INPUT STAGE; AND DIODE MEANS CONNECTED IN A DIRECT-CURRENT-CONDUCTIVE CIRCUIT BETWEEN SAID INPUT TERMINAL AND SAID COMMON TERMINAL SO AS TO COMPRISE A SHUNT PATH FOR INPUT SIGNAL VOLTAGE WITH RESPECT TO SAID INPUT CAPACITOR, SAID DIODE MEANS HAVING THE CHARACTERISTICS OF A SEMI-CONDUCTOR DIODE INCLUDING THE CHARACTERISTICS THAT IT IS FREE FROM THE GENERATION OF SPURIOUS SMALL VOLTAGES AND THAT ITS IMPEDANCE IS EFFECTIVELY INFINITE WITHIN THE NORMAL RANGE OF SIGNAL VOLTAGE AT SAID INPUT TERMINAL, AND THAT ITS IMPEDANCE DROPS TO A VERY LOW VALUE WHEN SAID VOLTAGE EXCEEDS SAID RANGE, THEREBY PREVENTING THE BUILDUP OF EXCESSIVE DIRECT VOLTAGE ON SAID CAPACITOR UPON THE APPLICATION OF INPUT SIGNAL VOLTAGE TO THE INPUT TERMINAL IN EXCESS OF SAID NORMAL VOLTAGE RANGE.