An analog sigma-delta modulator with shared operational amplifier for low-power class-D audio amplifier

Abstract

To minimize the power consumption of an analog sigma-delta modulator (SDM), a fifth-order loop filter of the SDM has been realized with only three operational amplifiers (op-amp). The analog SDM with shared opamp is applied to a class-D amplifier for a digital hearing aid. The class-D amplifier with the analog SDM has been realized in a standard 0.13-µm CMOS process. The maximum output power level of the class-D amplifier is 1.13-mW for a load with 46.5-Ω DC resistance. The total harmonic distortion+noise (THD+N) and the dynamic range (DR) of the class-D amplifier are 0.0038-% and 96-dB, respectively. The fifth-order analog SDM with shared op-amp consumes only 0.2-mW from a 1.2-V power supply.

Low-power Multi-bit Delta-Sigma Modulator based on Passive and Attenuationless Summation Scheme

“…In order to reduce this part of power consumption, passive summation schemes have been widely adopted. However, passive summation circuits directly parallel capacitors carrying the voltage signals of each branch [1, [16][17][18][19][20], which reduces power consumption but also causes attenuation of the summation result. This makes the design requirements for multi-bit quantizers more stringent, which is not desirable.…”