. The Bell System technical journal . as the current flowing from the grid to thefilament is reduced. That is, a change in the \oltage drop across This condition for stable equililuiuin will ,ilsi) Inshift around the loop is cfiiial to 2ir»; wlurc ii In- .ii ^.itislicil il llu- niinihcr. rcnii (\ 511 ilii- )i\k\ circuit resistiinci- causts a change f opposite si^n in theNoltagc drop across the plate circuit resistance, the two voltage dropsheing referred to the potential of the filament. The freciuency contrt>lunit is in the form of a series ci
. The Bell System technical journal . as the current flowing from the grid to thefilament is reduced. That is, a change in the \oltage drop across This condition for stable equililuiuin will ,ilsi) Inshift around the loop is cfiiial to 2ir»; wlurc ii In- .ii ^.itislicil il llu- niinihcr. rcnii (\ 511 ilii- )i\k\ circuit resistiinci- causts a change f opposite si^n in theNoltagc drop across the plate circuit resistance, the two voltage dropsheing referred to the potential of the filament. The freciuency contrt>lunit is in the form of a series circuit containing inductance, capacity,.md resistance. Two resistance elements are used for conplini; tn theinput and to the output of the amplifier. us tirst consider the properties of the vacuum tui)e Fig. 3 the voltage develoix-d across the junction A is plotted as afunction of the voltage across the junction B. us assume, forthe present at least, that this curve holds for all frequencies. Obviously. VOLTAGE AT Blig. S .Amplifier output tiri>lic- the voltage across the junction A depends upon the impedance lookinginto the frequency control unit, but if the resistance Ri is small incomparison with the resistance R, the voltage will be practicallyindependent of the frequency control unit. This curve representsa familiar characteristic of the vacuum tube amplifier. It showsthat as the voltage upon the grid of the first tube is increased, a pointis reached where the amplitude of the output is no longer propor-tional to the amplitude of the input. If this is carried far enough apoint is ultimately reached where a continued increase in the voltageon the grid fails to produce any further increase in the voltage acrossthe output. For our present purpose the data contained in thiscurve will be more useful if plotted in a less familiar form. 512 BELL SYSTEM TECHNICAL JOURNAL In Fig. 4 the ratio of the voltage across the junction B to the voltageacros
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
