Application of Fixator-Norator Pairs in Analog Circuit Design

Abstract

Recently Fixator-Norator Pairs (FNP) have been shown to be very powerful tools in designing analog circuits for multiple specs. These specs are separated into different areas of the design, and for each area a specific design methodology is introduced in this chapter. The areas mainly consist of designing for circuit biasing, gains, input and output impedances, active loads and current mirrors in ICs, and frequency responses and bandwidth for amplifiers. Very similar to a nullor, it is shown that the role of the fixator in an FNP is to provide a fixed and stable response to a circuit variable as specified by the design criteria. The norator, on the other hand, acts as a place holder for one or more circuit components that are needed to provide the requirements in the circuit to respond to spec, being held constant by the fixator. In designing for frequency and bandwidth, specifically, the mission is harder because of the complexity of the situation. It is shown that a model circuit helps in this case to provide the frequency response needed for the design. Since a model circuit is only for simulation purposes, it can be constructed from ideal components such as controlled sources, and it can be even built quite modular. As shown, the FNP methodology works for both linear and nonlinear circuits. However, for nonlinear circuits we need to keep the biasing situation unchanged during the AC design process. The circuit biasing may change when feedbacks are added to the original amplifier circuit, if not protected. In case needed, coupling capacitors are added to protect the circuit biasing. There are sections in the chapter, where each covers a separate feature and application of FNP in analog circuit design. Examples have also been worked out in rather details to show the role and significance of FNP in each application.