Abstract
Pulse density modulation (PDM) based class-D amplifiers can reduce non-linearity and tonal content due to carrier signal in pulse width modulation based amplifiers. However, their low-voltage analog implementations also require a linear loop filter and a quantizer. A PDM based class-D audio amplifier using a frequency-domain quantization is presented. The digital intensive frequency-domain approach achieves high linearity under low supply regimes. An analog comparator and a single-bit quantizer are replaced with a current controlled oscillator (ICO) based frequency discriminator. By using the ICO as a phase integrator, a third-order noise shaping is achieved using only two analog integrators. A single-loop, single-bit, class-D audio amplifier is presented with an H-bridge switching power stage, which is designed and fabricated on a 0.18 μm CMOS process with 6 layers of metal achieving a total harmonic distortion plus noise (THD+N) of 0.065% and a peak power efficiency of 80% while driving a 4-Ω loudspeaker load. The amplifier can deliver the output power of 280 mW.
Original language | English (US) |
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Pages (from-to) | 173-186 |
Number of pages | 14 |
Journal | Analog Integrated Circuits and Signal Processing |
Volume | 72 |
Issue number | 1 |
DOIs | |
State | Published - Jul 2012 |
Keywords
- Audio amplifiers
- Class-D amplifiers
- Frequency discriminators
- Sigma-delta modulation
ASJC Scopus subject areas
- Signal Processing
- Hardware and Architecture
- Surfaces, Coatings and Films