12-bit Sigma-Delta Modulator for Biomedical Wireless Applications

Abstract

A high-resolution, low-voltage sigma-delta ($\Sigma\ \Delta$) analog-to-digital converter (ADC) is required for the bio-medical application. A high-resolution first-order $\Sigma\ \Delta$ modulator is proposed in this paper. The operational amplifier of the proposed modulator is implemented by folded cascode common source (FC-CS) approach, which achieves the gain of 63 dB with a bandwidth of 1.3 MHz. The modulator is implemented with an OSR of 20, signal bandwidth of 2 MHz, and 80 MHz of sampling frequency. This designed modulator is appropriate for high-resolution medical applications in the 2.4 GHz ISM frequency band for IEEE 802.15.6/Bluetooth standard. The proposed modulator is designed in 65 nm bulk CMOS, providing the peak SNDR of 70 dB, ENOB of 12, bandwidth 2 MHz, and power consumption of 2.12 mW at 1.2 V supply voltage.