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Author:
Marco Gavesi |
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Preamble:
The Spice48G determines the dc operating point of the
circuit with inductors shorted and capacitors opened. Circuit
may contain resistor, diodes, BJT's, OPAMPs (operational amplifiers).
The program work in cooperation with SOLVESYS
- Sune Bredahl - Non-linear equation solver
library. The dc operating point determines the work zone
of non-linear device by the system of non-linear equations.
Each device are descripted by built-in models for the semiconductor
device, and the user need specify only the pertinent model parameter
values.
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Circuit Description: The
circuit to be analyzed is described by a set of elements cards. Each element in the
circuit is specified by an element card that contains the element name, the voltage nodes,
the current node, the parameters, the model, the value. Element will be enclosed in
"{" and "}" signs. Resistors
General form : { R I N1 N2 VALUE } where N1
and N2 are two voltage element nodes. VALUE is the
resistance (in ohms) and may be positive or negative but not zero.
Examples : { R IR V1 V2 100 } { R IR 10 0 1000 }
Node
Node card generating current node equation. The tag IA,
IB or IC can be also current node equations. The negative current will be enclosed in the
' ' signs.
General form : { J IA IB IC }
Examples: { J I1 I2 '-I3' } { J 'IA-IB' I2 I3} (cascade of current node
equations) { J '-I1' '-I2' '-I3' }
Bipolar Junction Transistor (BJT)
The bipolar junction transistor model in SPICE is an
adaptation of the simpler Ebers-Moll Model.
General form : { Q VB VC VE IB IC IE model IS betaF betaR VA ID },where: VB = base voltage
, VC = collector voltage, VE = emitter voltage, IB = base current, IC = collector current,
IE = emitter current, model type = NPN or PNP, IS = transport saturation current (default
= 1.0E-16), betaF = ideal maximum forward beta (default = 100), betaR = ideal maximum
revers beta (default = 1) , VA = Early voltage (default = infinite (1E+99)), ID is the
name of device in the circuit
Examples : { Q V1 V2 V3 I1 I2 I3 NPN 1E-15 100 1 1E99 Q1 } two parameters model {
Q V1 V2 V3 I1 I2 I3 PNP 1E-15 100 10 10 Q1 } three parameters modeln
OPAMP (Operational amplifier)
General form : { O V+ V- VU AD0 R0 I- I+ Iu VUM } { ONS
V+ V- VU AD0 R0 I- I+ Iu VUM } OPAMP in high gain zone { OSP V+ V- VU AD0 R0 I- I+ Iu VUM
} OPAMP in positive saturation { OSM V+ V- VU AD0 R0 I- I+ Iu VUM } OPAMP in negative
saturation
Where V+ = non inverting input, V- = inverting input, Vu = output voltage, AD0 = Open Loop
Gain (default AD0=10E5), R0 = Output resistance (default R0=10 W), I- = inverting current,
I+ = non inverting input current, Iu = Output current, VUM = Saturation voltage
Examples : { ONS V1 V2 VU 10E5 10 I1 I2 Iu 10 } { O V1 V2 VU 10E5 10 I1 I2 Iu 10
}
Diode
The dc characteristics of the diode are determined by the
parameter IS.
General form : { D I VA VB IS } where I = diode current, VA = anode voltage, VB = catode
voltage, IS = saturation current
Example : { D I1 V1 V2 1E-16 }
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DC Analysis:
At the end of this procedure the list of components
must be stored in a variable. (Ex : 'ES' STO).
Subsequently. you must go in the directory named DATI and
store correct value of termical voltage VT in the variable
named VT, store value of operating points. Now, you must go
in the up directory (default directory), and press the variable
ES (circuit description) and press button OP (operating point
calculation program). Now you are in the SOLVESYS
library program, press INIT to continue, specify the initial
values (e.g. all transistors are ON) and press SOLVE
to solve the system of non-linear equations. Finally, press
STK-> to copy all values in the stack window.
Example: Vcc=10V, VEE=-10V, R=1KW bF=70, bR=1 VT=25mV, IS=8fA, VUM=10V.
Two identical transistor with two parameters model (no Early effect) Opamp is ideal
without reactive effect.
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Problem: Calculate the V+ and V- voltage
in the dc operating point correspond to Vi1=-2.9V, Vi2=-3.7V
Example Step by Step:
Go to
Directory named DATI and store the RX, Vi2, Vi1 and VT
values |
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Specify the
circuit schematic in the stack:
{
{ Q Vi1 VC1 VE Ii1 IC1 IE1 NPN 8.E-15 70 1 1.E99 Q1 }
{ Q Vi2 VC2 VE Ii2 IC2 IE2 NPN 8.E-15 70 1 1.E99 Q2 }
{ J IE1 IE2 '-IR' }
{ R IR VE -10 1000 }
{ R IRX 10 VC1 RX }
{ R IR2 10 VC2 1000 }
{ J IRX '-IC1' '-I' }
{ J IR2 '-IC2' '-Ip' }
{ O VC2 VC1 Vu 1000000 10 Ip Im Iu 10 }
{ J I '-Im' Iu}
{ R Iu Vu VC1 1000 }
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Circuit Description in Stack
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Press OP
button to start analysis
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System of non-linear equations that describes the circuit:
18 non-linear equations
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Press OK
button to start SOLVESYS
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Specify the
initial values to solve the system
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Press SOLVE
button to start analysis
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After few
minutes, the system will be solved
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Press ->STK
button to copy values to stack
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The
calculated values in the stack are:
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The
USERRPL Code: EE (5546 bytes) |
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HTML
Documentation and program code in zipped format: spice48g.zip |
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References:
- Zsolt M. Kovacs Vajna, Alberto Leone, Introduzione
all'elettronica analogica in 50 Esercizi, Patron Editore Bologna (in Italian
language)
- P.W.Tuinenga, SPICE, A Guide to Circuit Simulation and
Analysis Using Spice, Prentice Hall
- W.Banzhaf, Computer Aided Circuit Analysis using
SPICE, Prentice Hall
- SPICE2G, User's Guide, C.L.U.P.
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