Research On Distortion Of Integrated Amplifier And Related Analog Circuits

Nowadays, the progress in information technology and the introduction of all kindsof international telecommunication standards make more strict demands on design ofanalog integrated circuits. One of the most important challenges is the improvement ofthe linearity of the analog integrated circuits. Therefore, as the crucial specification andcriterion, the reaseach of distortion has aroused wide concern of the academic andindustry worlds. The distortion of amplifier which serves as the the principal componentof analog circuits, is highly significant. The linearity of the amplifier plays an importantrole in determination wheather or not the design can satisfiy the demands.According to the above problems, in this disseratation, the distortion of singlestage output amplifier, the class-AB amplifier and the Miller compensated two stagetransconductance amplifier was used as object and it was modeled and investigated withthe help of the analyses of its causing mechanism. In addition, the distortion of servealmajor component of analog circuits related to amplifier, such as active RC lossyintegrator, fully balanced third-order Butterworth Gm-C filter were studied also. Themain contributions are as follows:1. The distortion factors of feedback single-stage amplifier were derived byexploiting the phasor method. Thanks to the consideration of intermodulationnonlinearity in the amplifier, the decision of the modeling was improved.2. The nonlinear coefficients of DC transfer characteristics of class-AB amplifierwere extracted by using the least square method and the distortion of this kind ofamplifier was modeled with these coefficients. The accuracy and flexibility of themodeling were verified by simulation.3. The nonlinear signal-flow-based method was proposed and employed to modelthe distortion of feedback two-stage amplifier compensated with Miller capacitor andnulling resistor. The impacts of intermodulation nonlinearity, parasitic capacitors andexternal configuration resistors on distortion behaviors were discussed. Thecharacteristic frequencies of the distortion factors were derived. The quantitativerelationships between distortion factors and external feedback resistors were obtained also.4. The distortion of active-RC lossy integrator with external loop excess phasecompensation was modeled with the support of the Volterrra series method. It fills thegap of distortion modeling of this kind of integrator.5. A block diagram method which can be used to model the Gm-C filter wasproposed and the distortion of a fully-differential third-order Butterworth filter wasevaluated by applying this method. This modeling not only keeps high precision butalso provides more insights and convenience.6. The empirical formulas for fitting the nonlinear DC transfer charactristics offully-differential amplifier was proposed and the iteration approach for calculating theswitched-capacitor Σ-Δ integrator and modulator was modified with the aids of theseempirical equations. The approach has speed advantage on the transistor levelsimulation by using commercial EDA tools and behavioral simulation by usingSimulink.