Environmental Engineering Reference
In-Depth Information
Chapter 2
COMPUTER FORMULATION OF
MIXED-MODE SWITCHING CIRCUITS
This chapter deals with computer-oriented formulation of mixed-mode
switching circuits. Section 1 investigates the modeling of switches. The
advantages and limitations of various switch models are examined. Sec-
tion 2 presents a historic perspective of the computer-oriented formu-
lation of mixed-mode switching circuits. We show that although many
computer-oriented formulation methods were proposed, only modified
nodal analysis (MNA) remains popular. This section also examines the
implementation of the computer formulation of mixed-mode switching
circuits using modified nodal analysis. Specifically, the matrix stamps
of elements used in modified nodal analysis formulation are developed.
Special attention is given to circuit elements with memory, as the en-
ergy stored in these elements is intrinsic to the operation of switching
circuits. The chapter is summarized in Section 3.
1.
Modeling of Switches
Mixed-mode switching circuits distinguish themselves from time-invariant
circuits by including switches. Switches appears physically in the form of
NMOS transistors or as a pair of CMOS transistors in externally clocked
circuits, such as switched capacitor networks and switched current net-
works, and diodes and thyristors in circuits with internally controlled
switches. They can be characterized at different levels of circuit ab-
straction, among which,
full-transistor model, voltage-modulated resistor
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