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BELL SYSTEM TECHNICAL JOURNAL 



In Fig. 4 the ratio of the voltage across the junction B to the voltage 

 across the junction A is plotted as a function of the \-oltage across 

 the junction A. This curve is obtained from the same data as the 

 curve of Fig. 3 and tells the same story. Assuming that this curve 

 holds for all frequencies a family of curves may be plotted for the 

 amplifier unit, as shown by the horizontal lines in Fig. 5. In these 



VOLTAGE AT A 

 Fig. 4 — .Amplifier gain characteristic 



curves the ratio of tiie voltage recci\ed b\ the unit to the \oIiagc 

 deli\ered by it is plotted against frequency. The numbers asso- 

 ciated with each curve indicate the voltage at ^, in arbitrary units, 

 for which the curve holds. 



A similar family of cur\es may be plotteil for tlic frcciueniN idnlrol 

 unit. Since the impedance of the series resonance circuit varies 

 will) frequency from relatively high values above and below the 

 resonance frequency to a minimum value at the resonance frequency, 

 it follows that, for a fixed voltage across the junction A, the current 

 through the inductance, the capacity and the resistance /?» will vary 

 with frequency. Consequently the voltage drop across the resistance, 

 which is impressed across the junction B, will \ar>- with frequency. 

 The relation between this \'ollage and frequency, for a fixed voltage 

 across the junction A, is given by the familiar resonance curve. 

 As the voltage across the junction A is increased, currents of con- 

 siderable magnitude may be caused to flow through the inductance, 

 particularly in the neighborhood of the resonance point. If this 



