
38
Power effiCienCy in wireless CommuniCations
3.4.2 Class B
e operation of a class B power amplifier is different than a class A
in that it operates at a zero quiescent current, hence the DC power is
small.is causes its efficiency to be higher than a class A power amplifier.
iscomes at the expense of the linearity of the power amplifier.
Figure3.10 shows how the class B amplifier operates. e output
power of the single-ended class B amplifier is
=⋅⋅
V
o
(3.19)
250
200
d
d
150
100
50
dq
0
250
200
150
100
50
0
0510
V
dd
V
ds
(V)
VGS5
VGS4
VGS3
VGS2
VGS1
15
(a)
20
0 0.2 0.4
Time (nsec)
0.6
0.8 1
l
Figure 3.10 (a) Load line and (b) current waveform for the ...