transition frequency; frequency at which small-signal forward current transfer ratio (common-emitter) extrapolates to unity (f_T)

The product of the modulus (magnitude) of the common-emitter small-signal short-circuit forward current transfer ratio, h_fe, and the frequency of measurement when this frequency is sufficiently high that the modulus (magnitude) of h_fe is decreasing with a slope of approximately 6 dB per octave. (Ref. IEEE Std 255.)

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