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Class G and charge-pump technologies maximize efficiency in boosted amplifiers

Posted: 12 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Class G? charge pump? boosted amplifier?

A common problem in portable audio applications is the limited supply voltage available to the speaker amplifier. Li-ion batteries are typically used in these audio systems, which produce 3.7V nominally. While a 3.7V supply is sufficient to run most elements of the system, the speaker amplifier requires more voltage to generate acceptable sound pressure levels. Consequently, most speaker amplifiers power transducers in a bridge-tied-load configuration, which allows twice the supply voltage to be applied to the speaker.

Although doubling the supply voltage to the speaker is sufficient in many cases, some applications require even more output power. Two examples are systems that either use piezoelectric speakers (which require high voltage drive) or require high sound-pressure levels (such as GPS devices). The only solution for these demanding audio applications is to boost the supply voltage, which typically requires a separate DC/DC boost converter and adds cost and complexity to the system.

The MAX9730 and MAX9788 Class G power amplifiers solve this supply-voltage problem by using a charge pump to boost the supply voltage. The MAX9730 specifically addresses traditional dynamic speakers, while the MAX9788 addresses ceramic speakers.

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