A THD-reduction high-efficiency audio amplifier using inverter-based OTAs with filter-output feedback

This paper presents an integrated low-voltage THD-reduction high-efficiency class-D audio amplifier using inverter-based operational transconductance amplifiers (OTAs). We propose a negative feedback loop which can compensate for external perturbations and improving output precision. The compensator increases the audio-frequency loop gain, and leads to a better rejection of audio-frequency disturbances. The use of inverter-based OTA and comparator provides low-voltage operation and low-power dissipation. The audio amplifier operates with a 1.5V supply voltage with maximum power efficiency of 90%. The proposed class-D amplifier was implemented using a TSMC [email protected] 1P6M CMOS process, and the active chip area is 1.87mm^2.

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