The effect of collector capacity on the transient response of junction transistors

The effect of collector depletion layer capacity on the transient response of junction transistors to a current input is calculated for the case of a resistive load. Expressions are given for the small-signal rise-time of the common-base, emitter, and collector configurations and for the large-signal turn-on and decay times of the common-emitter and collector configurations. The analysis shows that the transient durations under most conditions of operation are approximately (
1 + \omega_{\alpha}R_{L}C_{c}
) times those which would be predicted for the short-circuit output approximation reported by Moll [1]. Experimental results are reported which exhibit an excellent agreement with the analysis over a wide range of
\omega_{\alpha}R_{L}C_{c}
. An empirical examination has been made of the dependence of large-signal switching time on the range of operating point excursion. A satisfactory approximate representation of this dependence is provided by a first-order correction factor, which takes into account the functional dependence of ω
α
and C
c
on collector voltage.