PAPER SESSION 2: POWER STAGE TOPOLOGIES
AND IMPLEMENTATION
Improve PSRR and Output Power Capability by
Using a Boosted Class D Amplifier
Dominique Romeo
ON Semiconductor France
In mobile phone applications, Power Supply Rejection
Ratio (PSRR) and Output Power capability are key
parameters. In that kind of portable application, class
D amplifiers (CDA), thanks to a high efficiency and a
large output capability, are more and more popular.
However, compared to a class AB amplifier, the
PSRR is still one of the class D drawbacks. When a
state of the art class AB amplifier can achieve a
PSRR as high as �100 dB at 217 Hz and fully reject
supply noise like GSM burst, classical class D amplifier
difficultly go under �80 dB. Moreover, even if the
CDA Output Power capability is larger than class AB,
this output power is still dependent upon the battery
voltage level. This paper depicts the concept of
Boosted Class D Amplifiers (BCDA), which could be
an alternative to solve these two limitations: PSRR
and output power variation.
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