Frequency Variations of Current-Amplification Factor for Junction Transistors

In a grounded-emitter or grounded-collector connection of a junction transistor, the effective current amplification is proportional to the factor (1-¿)-1, where ¿ is the current-amplification factor of the transistor. As a result of the phase shift associated with a, the magnitude of (1-¿)-1 decreases rapidly with increasing frequency. It is shown that the magnitude of (1-¿)-1 is 3 db below its low-frequency value at a frequency of the order of magnitude of (1-¿0) times the frequency at which the magnitude of ¿ alone has decreased 3 db below its low-frequency value of ¿0. In addition, experimental results of measurements of phase and amplitude characteristics of ¿ as a function of frequency for several fused-impurity p-n-p junction transistors are presented and are compared with the variation of ¿ with frequency calculated in accordance with the theory of Shockley, et al.