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symbol for it is f
T
, but this one is sometimes taken to mean the
product of low-frequency h
fe
and bandwidth. As the bandwidth is
regarded as the frequency band up to the —3 dB point, this
Fig.
22.
JO
Simplified high-frequency
phasor diagram for a transistor,
derived from Fig. 22.9
interpretation of f
T
gives it the same value: 40x0.8 MHz in this
example. But this is only so in this rather over-simplified theory of
the relationship between /?
fe
and frequency, and in practice the
different definitions of /, and f
T
may result in slightly different
values.
The same zero-dB frequency is also normally nearly the same as
that at which is 3 dB down ...