A MASH2-2 Sigma Delta Modulator with NTF Zero Optimization Technique

In this paper, a high accuracy discrete-time sigma delta modulator (SDM) is presented. The multistage noise shaping (MASH 2–2) topology which provides a high-order noise shaping while avoiding instabilities is adopted. Unity signal transfer function (STF) which could lower the sensitivity to circuit imperfections is obtained through the feedforward path. Besides, the multibit quantizers are utilized to enhance the dynamic range (DR) and relax the performance requirement of the operational amplifiers. With the purpose of further minimizing the in-band noise power, the zeros of the noise transfer function (NTF) are optimized. A system level simulation based is verified with ideal blocks in SIMSIDES-TOOLBOX. The behavioral model level simulation results show a 14dB SNR improvement with the optimization.