MADCAT (MAtlab-Derived Circuit Analysis Tool)

 

 

About MADCAT:

 

MADCAT performs circuit analysis of linear dc and ac circuits.   Networks may contain resistors, capacitors, inductors, magnetically-coupled inductors, independent voltage and current sources, and controlled sources (voltage-controlled voltage sources, voltage-controlled current sources, current-controlled voltage sources, and current-controlled current sources).  Single-point dc analysis or dc sweep analysis may be performed; swept-frequency ac analysis may be performed with linear or logarithmic sweep. 

 

MADCAT was written as a senior project by Kau Teng Lim, who earned a BSEE from the University of Texas at Tyler in August, 2000.  MADCAT is intended for use in introductory courses in circuit analysis.  It was meant to be easy to learn and helpful in teaching concepts of network topology. 

 

Publications:

 

MADCAT has been described in publications:

 

D. M. Beams and Kau Teng Lim, Home-grown circuit analysis—MADCAT in the classroom. Presented at the 2003 Annual Conference

of the American Society for Engineering Education, Nashville, TN, June 23–25, 2003.  (also see PowerPoint presentation)

 

D. M. Beams and Kau Teng Lim.   MADCAT: A Student-Designed Simulator for Use in Introductory

Circuit-Analysis Courses.  Computers in Education Journal 14:4 (Oct–Dec 2004), 12–21. 

 

Using MADCAT

 

MADCAT requires that Matlab (The Math Works, Natick, MA) be installed on the user’s computer.  MADCAT is not currently available as a stand-alone executable file.

 

Networks are described by text files which may be created with any ASCII text editor (e.g., Notepad).  An example circuit file and the corresponding schematic are shown below.  The active text of the circuit is terminated with an “.end” statement.  Text beyond this is ignored and may be used for comments as in the example below. 

 

Ovals indicate assigned node numbers in the schematic below.  Nodes need not be numbered sequentially; “0” is reserved for ground.  Arrows indicate the presumed directions of branch currents.

 

Each element in the schematic is represented by one line in the text file; each line describing a circuit element follows a common format.  The element name is in the first column.  Element types R (resistor), C (capacitor), L (inductor), M (mutual inductor), V (independent voltage source), I (independent current source), E (VCVS), F (CCCS), G (VCCS), and H (CCVS) are recognized.  Current is presumed to flow into the element at the FROM node, flow through the element, and exit at the TO node.  For example:  

 

Element            FROM             TO                   Branch             Element

name                node                 node                 current              value

 

R3                    40                    0                      7                      3k

 

Element values may have unit multipliers.  Multipliers recognized are p or P (pico-), n or N (nano-), u or U (micro-), m (milli-), k or K (kilo-), M (mega-), and g or G (giga-).  “+” and “–“ signs are also allowed.  Other letters are ignored; thus it is equivalent to write the voltage of the independent voltage source Vsrc in the example below as “1,” “+1V,” or “+1.0V.”

 

Controlled sources require additional information.  Current-controlled sources require that the controlling branch current be specified; the “4” in the description of F1 below indicates that the output current of the current-controlled current source is controlled by the current in branch 4.  Voltage-controlled sources require a pair of node numbers to represent the + controlling node and the – controlling node. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C1        2         0        3        10pF

C2        2         40      5         2pF

R1        1         2        2         600                

R2        2         0        4         2k

R3       40        0        7         3k

Vsrc    1         0         1        5mV

F1       40        0        6        250        4       

.end

 

File for ac analysis of a common-emitter amplifier for MADCAT 2000.

The label of the controlling branch current [I(4)] of current-controlled

current source F1 is entered in the fifth column.  This circuit is an ac model

of a common-emitter transistor including base-emitter capacitance (C1), base-

spreading resistance (R1), small-signal ac resistance of the base-emitter junction

(R2), Miller capacitance (C2),a current-controlled current source (F1), and a

load resistance from collector to ground (R3).  A voltage source (Vsrc  drives the

network.  Output (collector) voltage is at node 40.

 

 

Results of the ac analysis of the common-emitter amplifier are displayed below.   The upper graph is the voltage gain in dBV (decibels with respect to 1V); the lower graph gives phase in degrees. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Download the archive and view the included file madcat_readme.txt for installation and running instructions.  A user’s guide is also available in .zip format.

 

Send comments or questions about MADCAT to dbeams@uttyler.edu.