A design of 2nd order DT sigma-delta modulator for medical implants

Abstract

This paper proposes the design of a second order sigma delta modulator (SDM) to be used in medical implants for conversion of low frequency human body analog signals into digital format. The lifetime of a medical implant is governed by the power consumed by various blocks in it, of which the block consuming maximum power is the Analog to Digital Converter (ADC). This paper aims at designing a power optimized ADC by making use of CMOS operational trans-conductance amplifier(OTA) whose transistors are biased in sub threshold conduction region by making use of body biasing technique. The modulator thus implemented consumes a power of 4.6 µW from a 0.9V power supply. The modulator achieves an SNR of 64dB for a bandwidth of 500 Hz.