Computer program simulates the time domain response of an electronic circuit to an arbitrary forcing function. CIRCUS uses a charge-control parameter model to represent each semiconductor device. Given the primary photocurrent, the transient behavior of a circuit in a radiation environment is determined

Moore, W. T.

Steinbert, L. L.

English

NASA Technical Reports Server

December 1968
	 Brief 68-10416 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
CIRCUS—A Digital Computer Program for Transient Analysis

of Electronic Circuits 
The problem: 
To provide a means for studying the effect of tran-
sient nuclear radiations on electronic circuits, since 
it is necessary to prevent damage to or spurious output 
from many types of circuits. 
The solution: 
A computer program which simulates the time 
domain response of an electronic circuit to an arbi-
trary forcing function. CIRCUS uses a charge-control 
parameter model to represent each semiconductor de-
vice. When given the primary photocurrent induced 
in the semiconductor devices, the transient behavior 
of a circuit in a radiation environment can be de-
termined. 
How it's done: 
Since any circuit is completely defined by the com-
ponent values and by the way in which the com-
ponents are interconnected, it is apparent that a 
digital computer can be used to construct the circuit 
equations from a physical circuit description. CIRCUS 
follows this approach, setting up the time-domain 
equations from a topological description of the net-
work. CIRCUS finds the steady-state initial condi-
tions by setting the differential equations to zero, 
then evaluates the transient solution by numerical in-
tegration of the differential equations.
The program output includes the input data and 
columnar listings of network variables vs time. Vir-
tually any circuit variable including currents and 
voltages internal to the semiconductor devices, may 
be displayed. Although no plotting capability is ordi-
narily supplied with CIRCUS, provisions have been 
made for saving variables on tape for subsequent plot-
ting or further analysis by other programs. 
Notes: 
I. This program is written in Fortran H and Assembler 
for use on the IBM 360 computer. 
2. Inquiries should be made to: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B68-10416 
Patent status: 
No patent action is contemplated by NASA. 
Source: L. L. Steinbert, and William T. Moore 
of The Boeing Company 
under contract to 
Marshall Space Flight Center 
(M FS- 15002) 
Category 06 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
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CIRCUS--A digital computer program for transient analysis of electronic circuits

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