A low-power sigma-delta modulator based on high-order op-amp sharing technique for speech communication

Abstract

In this paper, a novel idea of sigma-delta modulator (SDM) is proposed based on our high-order (greater than or equal to 4th order) op-amp sharing technology. The operation timing, adder, integrator structure and the switched-capacitor op-amps common-mode negative-feedback of the conventional single-loop cascade-of-integrators with feedforward (CIFF) modulator are improved, so that the nth-order integration function can be accomplished by using one op-amp. Finally, a high-precision and low-power sigma-delta modulator for speech communication is realized. The proposed 4th-order CIFF sigma-delta modulator based on our high-order op-amp sharing is utilized in 0.18 µm standard CMOS process and occupies an area of 0.218 mm2. Simulation results show that the SNDR is 103.91 dB and the ENOB is 16.97 bits with a sampling rate of 2.56 MHz, an oversampling ratio of 256, and signal bandwidth of 5 kHz. Proposed modulator has a supply voltage of 5 V and costs a power consumption of 2.29mW. The power consumption of proposed op-amp sharing idea is 29.67 % less than that of the conventional case.