is just the voltage difference between the collector and emitter, i.e.,
.
Well, and
are the same voltage. But indeed, voltage drops
must sum up to a total, by Kirchoff's Loop Rule:
referring to the transistor switch in Eggleston Fig 4.5,
you can write
.
can also be written as
(maybe this is
what you meant?), although this is not especially useful for
analyzing this switch.
Yes, could say that can be controlled for this switch by controlling the voltage at the base and
(and
). By choosing
, you effectively set
and
(according to the graphical solution depicted in Eggleston Fig. 4.6). This
then determines which curve from Fig. 4.7 applies. Along with the choice of
, this determines both
and
, which can be found from the graphical solution depicted in Fig. 4.7.
(Note that so long as , and hence
, are large enough, the values of
and
will be in the saturation parts of the curves in Fig. 4.7, and so will be only weakly dependent on the exact value of
.
will be small, and
large, where all the curves scrunch together.)