
205
b b
Fig. 12.18 Common-base amplifier circuit and phasor diagrams for comparison with
those for the other modes (Fig. 12.16)
for comparison with Fig. 12.16, and again we see the phasor diagram
is the same except for the encircled point marking the common
electrode. The voltage diagram shows at once that only common
emitter gives a signal inversion. Study of the three phasor diagrams
helps one to see how the common-emitter gives both voltage and
current gain, whereas common-collector gives only current gain and
common-base only voltage gain. The obtainable power gain of the
common-emitter mode is therefore obviously much greater than tha