Analysis of analog sampled data circuits

Abstract

Complex systems consist of a core of digital signal processing (DSP) buffered from external environments by analog interface circuitry. "Analog sampled data" circuits can be predominantly found in the data conversion portions of these mixedmode integrated circuits. Delta-Sigma modulator is an example. Analog sampled data circuits also perform signal processing tasks, and are used in many filtering applications. Switched-capacitor, and switched-current circuits are the examples of these applications.

Sampled data circuits are dual time systems that contain a rapidly varying clock and a slowly varying input signal. As a result, most of the simulation effort is dedicated to the transient analysis at switching instants, where information is usually not needed. The important required information is the response of the circuit at the end of the clock period, when it reaches the steady state. Searching for a method that can provide the solution of the circuit at discrete instants of time led to the "sampled data simulation" technique (l].

This thesis looks at different aspects of analog sampled data systems. It extends the idea of sampled data simulation to provide an accurate and efficient method of computing the time domain sensitivity of linear circuits. The method is applied to sensitivity analysis of an important class of sampled data systems, Delta Sigma modulators. We also provide efficient methods for analysis of switched networks, including the group delay and group delay sensitivity of periodically switched linear networks in general, and harmonic distortion of switched-current circuits in particular. Sources of distortion in switched-current circuits are examined, and both upper and lower bounds are derived on total harmonic distortion of a current memory cell.