Radio Frequency Integrated Circuit Design - Webs

382 Radio Frequency Integrated Circuit Design
Figure 10.34 Class F amplifier driving a class E amplifier.
Figure 10.35 Class G amplifier.
This topology uses amplifiers powered from different supplies. For lowlevel
signals, the lower supply is used and the other amplifier is disabled.
Class H uses a linear amplifier, such as a push-pull class B amplifier as
shown in Figure 10.36, to amplify the signal. However, its power supplies track
the input signal or the desired output signal. Thus, power dissipated is low,
since the driver transistors are operated with a low-voltage V CE. As a result,
the efficiency can be much higher than for a class A amplifier.
The power supplies use a highly efficient switching amplifier, such as the
class S shown later in Section 10.10. Noise (from switching) is minimized by
the power supply rejection of the linear amplifier.