What is the term for the frequency at which the grounded-base current gain of a bipolar junction transistor has decreased to 0.7 of the gain obtainable at 1 kHz?

Explanation

Alpha is the common-base, or grounded-base, current gain, so the frequency at which that gain has dropped to about 0.7 of its low-frequency value is the alpha cutoff frequency. Beta cutoff frequency is the corresponding figure for common-emitter gain, and the remaining two names are not standard transistor parameters.