An Ultra Low-Power Delta-Sigma Modulator Using Charge-Transfer Amplifier Technique

Abstract

In this paper, an ultra low-power delta-sigma (DeltaSigma) modulator applying charge-transfer amplifier (CTA) technique for voice-band applications is presented. Both the fully-differential charge-transfer amplifier and integrator are developed for higher dynamic range of the modulator. A 67 dB of the peak SNR within a 4 kHz of bandwidth is reached in the presented modulator under a 2.5 MHz of sampling rate. The prototype circuit has been implemented in a 0.18 mum 1P6M CMOS technology. The chip area excluding PADs is 0.50 times 0.28 mm2. Due to its zero static current of CTA, only dynamic power is consumed in the circuit. The power consumption of the analog part of the presented second-order DeltaSigma modulator is only 3.4 muW. The total power consumption of the whole modulator is 36 muW at a 1.8 V of supply voltage.