Contents of the NETWORK.DOC file
FBN Software proudly presents Network. Network is an analysis tool used to
perform an AC spectral analysis of an electrical network. The program does
this by using Kirchoff's laws to solve for the network node voltages and
What can I use Network for? Its primary application is to obtain the frequency
response of an electrical network. It can be used to analyze active and
passive filter implementations. It is a mini SPICE program without all of the
bells and whistles. With NETWORK you can prototype a circuit on your computer
and obtain insight on the actual operation of the real electrical network. You
can vary parameter values and determine their effect on the network's
Network presently allows a maximum of 30 NODES. All node voltages are
referenced to NODE 0 (electrical ground). The following components can be used
in the circuit : Resistors (60 max.), Capcacitors (60 max.), Inductors (60
max.), Amplifiers (10 max.), FET's (30 max.), and Transistors (30 max.).
Included on the disk is a sample network that has been saved to disk :
TEMP.DTA. This is a 4 node bandpass active filter made up of the following
C1 - 0.1
| R2 - 10k |
| | |
| C2 - 10 | | . |
| | | . |
Input (1)--/\/\/\/\---(2)-----| |----(3)---| - . + |
R1 - 1K . | . ------- (4)
> ------------| + .
R3 - 100 < | | .
> | | A1
The opening screen of network gives you the option of entering your network
components manually or from a saved file. If you type "D" (or "d") to this
response and provide the sample file name it will load. You then have the
option of editing component values and/or adding new components to the network.
The manual component entry asks you for the input and output node and then
asks for component values and node connections. After the last component has
been entered (component type), the program enters into the edit mode so you can
review and correct any entry errors you might have made.
The program then enters into the response calculation mode. This mode will
calculate the output You will be asked for a start frequency, a stop or end
frequency, and the frequency step size. The sweep can be linear (equal step
size) or logarithmic (equal steps on a log scale). If you want output to the
CRT or to a line printer. The program will then output the network response in
dB and phase angle in degrees for each frequency step. You also have the
option of saving the sweep output data to disk for input to a plotting
The frequency response (1 Hz - 10KHz) of the network in logarithmic frequency
steps has been saved in file TEMP.PLT. If you are using a CGA card for video
output, you can plot this response on your CRT using the program PLOTFL.EXE
that I have included on the disk. The program PLOTFL.EXE automatically adjusts
for linear or logarithmic frequency scale. The PLOTFL.EXE graph can also be
output to a graphics printer via the Shift-PrtSc key if you have loaded
GRAPHICS.COM (DOS Utility) before running the program.
After the frequency response has been output you will view a menu with the
option to run a new sweep, Edit/modify component values, or save the network to
disk. This feature lets you change circuit values to determine their effect on
the network's response or lets you expand a portion of the frequency sweep in
order to obtain higher output resolution.
The best way to learn how to use the program is to run it. View the file
TEMP.PLT in order to obtain a feel for what the network response is. Then run
NETWORK and load TEMP.DTA. Answer "N" (or "n") to all the edit questions and
try out the various sweep modes. Then try modifying some component values
(R3 is a good candidate) and see what effect the change has on the network
response. You can save the sweep outputs to disk if you want to or just
observe the changes on the screen and make a mental note of what happens.
If you save the sweeps to disk, use a different file name for each sweep. I
personally prefer to view the numbers rather than the graphics because it
gives me a better feel for what the actual values and response changes are.
The graphics plot is good for reports and for presentations.
Hints : For convenience capacitor values are input in micro farads. Diodes or
switches are not valid circuit components since the program is used for linear
network analysis. Diodes are assumed to be "Ideal" switches which are turned
on and have 0 resistance and can therefore be replaced by a short. If you want
to use a diode, approximate the diode with a small resistor which is equal to
the forward resistance of the diode (10 ohms or so). The amplifiers are
provided with differential inputs and outputs. Be sure that you use the proper
output in feedback circuits (negative feedback is a network between +output
and -input). The amplifiers (as provided) have infinite bandwidth. You can set
their open circuit voltage gain and output short circuit impedance. If you
want to add a gain-bandwidth limitation to an amplifier place a capacitor to
node 0 from its output. The amplifier response will then be band limited by
the RC time constant of the capacitor and the amplifier's output resistance
(Gain-Bandwidth = A/(2*pi*RC), where A is the Open circuit voltage gain of the
amplifier). Capacitors can also be added in parallel with FET source resistors
and Transistor collector resistors to limit the frequency response of these
Suggestions : Since the program uses matrix arithmetic to solve for the
response, much faster response is obtained for small networks than for larger
ones. If you have a large network try analyzing the network response by
breaking it into parts and determine how each part works before attempting the
final solution. NETWORK.EXE has been compiled using QB 4.0. QB 4.0 emulates
the 8087 chip, if one is not installed in your machine, which can slow down
Problems & Freeware Pitch : I offer this program to the general public as
"Freeware". By this I mean you can make copies of the ARC file and give them
to your friends. Just be sure to include all files (Including NETWORK.DOC) in
NETWORK.ARC. If you have problems and want support, I'll provide it to you for
a negotiable fee (depending on the difficulty of the problem). If you want to
modify NETWORK on your own (or you're just curious) I'll provide you with the
source code for NETWORK (and to PLOTFL) on a 360k 51/4 inch disk for a $10.00
Who am I and where do you send your money :
Send checks (no plastic) to :
William L. Gill
12713 Brunswick Lane
My qualifications : I am an Electrical Engineer with 27 years of experience.
My specialty is Signal Processing. I am a former applications engineer for
Westinghouse Integrated Circuits. I have approximately 15 years of part time
teaching experience (Application of Digital Integrated Circuits, and the
Application of Linear Integrated Circuits). So I have a strong background in
circuit analysis and performance.
Why am I doing this ? I don't really expect to make money from this program.
It is an engineering program and should therefore have a limited appeal. I
think it provides a tool that some of you will want to try. The fees that I am
imposing are to prevent "nuisance calls".