Analysis
of the modified MOS Wilson current mirror: a pedagogical exercise in
signal flow graphs, Mason's gain rule, and driving-point impedance techniques
- Spencer, R.G.
Dept. of Electr. Eng., Texas A&M; Univ., College Station, TX, USA
This paper appears in: Education, IEEE Transactions
on
On page(s): 322 - 328
Nov. 2001
Volume: 44 Issue: 4
ISSN: 0018-9359
References Cited: 6
CODEN: IEEDAB
INSPEC Accession Number: 7124322
Abstract:
A pedagogical analysis of the modified MOS Wilson current
mirror using signal flow graphs (SFGs), Mason's gain rule and
driving-point impedance (DPI) techniques is presented as an exercise
for undergraduate electrical engineering students learning to analyze
transistor-level circuits with multiple-feedback loops. While students
often prefer the SFG representation for single feedback loops, they
often abandon it in favor of the more familiar nodal analysis methods
for multiple loops. Yet these methods can be long and cumbersome and
contribute little to intuition. In an attempt to preserve the intuitive
grasp of tradeoffs, this paper presents an exercise of several
well-established analytical techniques for generating and analyzing
SFGs. The modified Wilson current mirror is used to compare three
analytical approaches: (1) fundamental laws with brute-force algebra;
(2) fundamental laws with Mason's gain rule; and (3) DPI technique with
Mason's gain rule. The concepts reinforced in this paper include: (1)
tradeoffs between gain and other quantities such as output resistance
or bandwidth; (2) how Mason's gain rule simplifies the analysis of
closed-loop gain; and (3) how DPI techniques simplify the generation of SFGs.
Index Terms:
electrical engineering education; MOSFET; current mirrors;
circuit feedback; signal flow graphs; teaching; MOSFET circuits;
network analysis; electric impedance; pedagogical analysis; modified
MOS Wilson current mirror; signal flow graphs; Mason's gain rule;
driving-point impedance; undergraduate electrical engineering students;
transistor-level circuits; learning; multiple-feedback loops;
tradeoffs; closed-loop gain