Design Of The Third Order Cascaded Sigma-Delta Modulator

The interest for sigma-delta modulators based on switched-capacitor(SC)circuit has significantly increased in recent years. A sigma-delta modulator provides a robust means of implementing a high-resolution converter architecture in scaled complementary metallic oxide semiconductor (CMOS) processing and very large scale integration technology, which is more suitable for implementing fast digital circuits than accurate analog circuits. The dissertation contains two main parts. First, this dissertation proposes a new body-effect compensated switch configuration for low voltage, low distortion SC applications. The proposed circuit allows rail-to-rail switching operation for low voltage SC circuits and has a better total harmonic distortion than the conventional bootstrapped circuit by 19 dB. Second, a 2-1cascaded sigma-delta modulator is suggested to provide a means for performing the high-resolution analog-to-digital conversion. The design of the transfer functions, system and circuits needed to realize a 2-1 cascaded sigma-delta modulator are explored. Non-idealities for circuit implementation are investigated. After discussing system-level considerations, a switch-capacitor integrator as the key circuit building block in sigma-delta modulator is explored. Given these circuit level specifications, the choice of operational amplifier topology is fixed; quantities such as dc gain, settling time, thermal noise and slew rate may be analyzed.The organization of the paper is arranged as follow:Chapter 1 is the motivation and brief summary of the research.Chapter 2 reviews the basic building blocks that comprise switched capacitor circuits. These building blocks are operational amplifiers, capacitors, switches, and non-overlapping clocks.Chapter 3 gives a brief overview of applications for switched-...