Low-Pass Sigma Delta Modulator for High Temperature Operation

Abstract

In this work, a design of 3rd-order sigma-delta modulator has been presented in details. It is capable of operating in high temperature environment (above 200 degrees). The input signal bandwidth is 250 Hz and sampling frequency is 128 kHz. It applies switched capacitor CIFB architecture with additional feed forward path to minimize the signal swing of internal stages. Meanwhile, by applying several high temperature design techniques, issues caused by the decreases of mobility and threshold voltage have been resolved. Over the temperature range from 0 to 300 degrees, the designed fully differential amplifier shows a steady gain above 63dB and the overall system achieves a steady SNR of 87 dB.