The theory of the effects of feedback on input and output resistance
is given in Sec.
12.5;
now we can glance at it again with particular
reference to amplifiers. Usually we would be glad to increase the
input resistance of a bipolar transistor so as to make it as nearly as
possible voltage-operated, more like an
f.e.t.
or valve. We saw in
Sec.
12.9
how a great increase is obtainable by working it in
common-collector (or emitter-follower) mode, and in Sec.
19.14
a
further increase by using a pair of transistors in this way. The effect
is produced by what amounts to total negative feedback; all the
outpu ...
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