
191
DA
= h
f
i
b
ι
AD
=
-h
f
i
b
L
-
iD
J
(a) (b)
Fig. 12.5 At (a), Fig. 12.4 is adapted for phasor diagrams (b)
So far an n-p-n transistor has been assumed, but no polarity
changes in equivalent circuit diagrams are needed for p-n-p types,
because when they are all reversed they are still relatively the same.
That is why it is possible to use one-way arrows for a.c. signals,
which are reversing all the time. But in circuits with reactances,
where phase relationships are not just simple positive or negative,
arrows can be confusing, whereas the notation explained in the latter
part of Chapter 5 is always unambiguous.
We next have to consider the inpu ...