A combined interpolatorless interpolation and high accuracy sampling process for digital class D amplifiers

We propose a novel combination of an ´interpolatorless´ interpolation technique with a high accuracy sampling process for low-power low-distortion digital class D amplifiers. This novel technique has the advantage of reducing the computational complexity of the usual two-step method (input signal interpolation cum sampling process). The complexity of this proposed technique is approximately equivalent to the complexity of the sampling process computation. Our proposed technique employs a 2^nd-order Lagrange interpolation polynomial and a Newton-Raphson method. We propose an initial guess for the Newton-Raphson method that produces an accurate estimation of the sampling process output in only one iteration. The simulated complete class D amplifier features low-power dissipation (∼56 μW, estimated @ 1.1 V, 0.35 μm CMOS) and relatively high signal-to-noise+distortion ratio (85.6 dB FS @ 4 kHz bandwidth), thereby rendering it appropriate for a hearing aid device.