Ming Xin Song

A Sigma-Delta Modulator System Design with 1-1-1 Mash Structure

This paper designs a three cascaded sigma-delta modulator with using mash structure. Analysis of gain coefficient of each module and simulate the modulator for the behavioral level. In 0.5μm CMOS process conditions, the input signal bandwidth is 20 kHz, oversampling rate is 256, SNR of the simulation model can get 100.5 dB, and accuracy is greater than 16 bit. Compared with other structures of the modulator, it has more stable and more dynamic range, so it can be applied to audio-frequency circuit.

Dielectric Charging Failure Analysis of RF-MEMS Switch

MEMS devices commercialization is hindered by reality problems. Among them main problem is caused by dielectric charging. This paper studies charging model and charges distribution which are constructed on adhesion failure. Lifetime prediction formula is given. Simulation results show that under the condition of low driven voltage requirement, lifetime is bigger than 1000 hours when elastic coefficient (K) adopts 4-16N/m, 0.4-1μm for dielectric thickness, 2-5μm for plate distance and S3iN4 as dielectric material. At last, C-V performances inflected by dielectric charging is studied by theoretical calculations and analyzing positive or negative charging respectively.

Design of High Gain CMOS Folded Cascode Operational Amplifier

A high-gain folded cascode operational amplifier is presented. Structure of folded cascode operational amplifier and manual calculations are discussed in detail. Folded cascode structure for the input stage is adopted. Folded cascode structure can increase the gain and the value of PSRR. Folded cascode structure can also allow self-compensation at the output. The operational amplifier is designed in 0.35μm CMOS process with 5V power supply. The operational amplifier has high-gain and work steadily. The results of SPICE simulations are shown that the operational amplifier achieved dc gain of 110dB with unity-gain bandwidth of 74.3MHz and phase margin of 54.4 degree.