Switching amplifier using a GaN field effect transistor for sound generator based on piezoelectric polymer

22.2 multichannel sound system has been launched in a satellite broadcasting since December 2018 in Japan. For installing such multichannel sound systems to home, an audio reproduction system is desired to be small and light weight. Although piezoelectric polymer has been regarded suitable for a thin and lightweight loudspeaker, piezoelectric polymer generally requires higher applied voltage to drive than a dynamic loudspeaker. Hence, we have adopted a switching amplifier to downsize the amplifier circuit and a GaN field effect transistor (FET) to generate enough voltage to drive the piezoelectric polymer without a transformer. The developed switching amplifier has successfully realized higher voltage and lower harmonic distortion compared to one made of a common Si FET.

Authors: Takehiro Sugimoto (NHK) and Kazuho Ono (NHK)