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OCS : Octave Circuit Simulator
History and Motivation
Problem Formulation
Data Structure
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Tutorials
A CMOS AND GATE
Here we show how to set up the simulation of the CMOS AND gate in the figure. The circuit has
- 9 Elements
- 6 MOSFETs (3 n-type + 3 p-type)
- 3 Voltage sources
Below we show three methods for constructing the circuit data structure
Once the circuit data structure is loaded the simulation can be started by the following commands
| Code: Run the AND gate simulation |
x = [.5 .5 .33 .66 .5 1 0 0 1 ]';
t = linspace (0, .5, 100);
pltvars = {"Va", "Vb", "Va_and_b"};
dmp = .2;
tol = 1e-15;
maxit = 100;
out = tst_backward_euler (outstruct, x, t, tol, maxit, pltvars);
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Click on the figure to the right to see the simulation results
Build the AND GATE structure directly
| Code: Build the AND GATE structure via an Octave script |
## NLC
# n-type
outstruct.NLC(1).func = "Mnmosfet";
outstruct.NLC(1).section = "simple";
outstruct.NLC(1).nextvar = 4;
outstruct.NLC(1).npar = 3;
outstruct.NLC(1).nparnames = 3;
outstruct.NLC(1).parnames = { "k", "Vth", "rd"};
outstruct.NLC(1).pvmatrix = [1.0000e-04 1.0000e-01 1.0000e+07
1.0000e-04 1.0000e-01 1.0000e+07
1.0000e-04 1.0000e-01 1.0000e+07];
outstruct.NLC(1).vnmatrix = [1 3 4 0
2 0 3 0
4 0 5 0];
outstruct.NLC(1).nintvar = [0 0 0];
outstruct.NLC(1).osintvar = [0 0 0];
# p-type
outstruct.NLC(2).func = "Mpmosfet";
outstruct.NLC(2).section = "simple";
outstruct.NLC(2).nextvar = 4;
outstruct.NLC(2).npar = 3;
outstruct.NLC(2).nparnames = 3;
outstruct.NLC(2).parnames = { "k", "Vth", "rd"};
outstruct.NLC(2).pvmatrix = [-1.0000e-04 -1.0000e-01 1.0000e+07
-1.0000e-04 -1.0000e-01 1.0000e+07
-1.0000e-04 -1.0000e-01 1.0000e+07];
outstruct.NLC(2).vnmatrix = [ 1 6 4 6
2 6 4 6
4 6 5 6];
outstruct.NLC(2).nintvar = [0 0 0];
outstruct.NLC(2).osintvar = [0 0 0];
# Va and Vb
outstruct.NLC(3).func = "Mvoltagesources";
outstruct.NLC(3).section = "sinwave";
outstruct.NLC(3).nextvar = 2;
outstruct.NLC(3).npar = 4;
outstruct.NLC(3).nparnames = 4;
outstruct.NLC(3).parnames = {"Ampl", "f", "delay", "shift"};
outstruct.NLC(3).pvmatrix = [0.50000 1.00000 0.00000 0.50000
0.50000 2.00000 0.25000 0.50000];
outstruct.NLC(3).vnmatrix = [ 1 0
2 0];
outstruct.NLC(3).nintvar = [1 1];
outstruct.NLC(3).osintvar = [0 0];
## LCR
# Vdd
outstruct.LCR(1).func = "Mvoltagesources";
outstruct.LCR(1).section = "DC";
outstruct.LCR(1).nextvar = 2;
outstruct.LCR(1).npar = 1;
outstruct.LCR(1).nparnames = 1;
outstruct.LCR(1).parnames = {"V"};
outstruct.LCR(1).pvmatrix = 1;
outstruct.LCR(1).vnmatrix = [6 0];
outstruct.LCR(1).nintvar = 1;
outstruct.LCR(1).osintvar = 2;
##
outstruct.namesn = [1 2 5 6 7 8 9];
outstruct.namess = {"Va", "Vb", "Va_and_b", "Vdd", "I1", "I2", "I3"};
outstruct.totextvar = 6;
outstruct.totintvar = 3;
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Build the AND gate circuit structure parsing an IFF netlist
| Code: Load the AND circuit structure parsing an IFF netlist |
outstruct = prs_iff ("and");
|
| Code: IFF netlist for the AND gate (.cir file) |
% 0.1b1
% A Simple CMOS AND GATE
%
% N-Mosfets
% There are 3 N-Mosfets
Mnmosfet simple 4 3
3 3
k Vth rd
1e-4 0.1 1e7
1e-4 0.1 1e7
1e-4 0.1 1e7
1 3 4 0
2 0 3 0
4 0 5 0
%
% P-Mosfets
Mpmosfet simple 4 3
3 3
k Vth rd
-1e-4 -0.1 1e7
-1e-4 -0.1 1e7
-1e-4 -0.1 1e7
1 6 4 6
2 6 4 6
4 6 5 6
%
% Input voltage sources
Mvoltagesources sinwave 2 4
2 4
Ampl f delay shift
0.5 1 0.0 0.5
0.5 2 0.25 0.5
1 0
2 0
END
%
% Power supply
Mvoltagesources DC 2 1
1 1
V
1
6 0
END
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| Code: IFF netlist for the AND gate (.nms file) |
% 0.1b1
1 Va
2 Vb
5 Va_and_b
6 Vdd
7 I1
8 I2
9 I3
|
| Code: Model evaluator file for simple MOSFET models |
function [a,b,c] = Mnmosfet (string, parameters, parameternames, extvar, intvar, t)
switch string
case 'simple',
rd = 1e6;
for ii=1:length(parameternames)
eval([parameternames{ii} "=",...
num2str(parameters(ii)) " ;"])
endfor
vg = extvar(1);
vs = extvar(2);
vd = extvar(3);
vb = extvar(4);
vgs = vg-vs;
vds = vd-vs;
if (vgs < Vth)
gm = 0;
gd = 1/rd;
id = vds*gd;
elseif ((vgs-Vth)>=(vds))&(vds>=0)
id = k*((vgs-Vth)*vds-(vds^2)/2)+vds/rd;
gm = k*vds;
gd = k*(vgs-Vth-vds)+1/rd;
elseif ((vgs-Vth)>=(vds))&(vds<0)
gm = 0;
gd = 1/rd;
id = vds*gd;
else # (i.e. if 0 <= vgs-vth <= vds)
id = k*(vgs-Vth)^2/2+vds/rd;
gm = k*(vgs-Vth);
gd = 1/rd;
endif
a = zeros(4);
b = [ 0 0 0 0;
-gm (gm+gd) -gd 0;
gm -(gm+gd) gd 0;
0 0 0 0];
c = [0 -id id 0]';
break;
otherwise
error(["Mnmosfet: unknown option " string]);
endswitch
endfunction
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Build the AND gate circuit structure parsing a .spc file
| Code: Load the AND circuit structure parsing a .spc file |
outstruct = prs_spice ("and");
|
| Code: The .spc file for the CMOS AND gate |
* AND (simple Algebraic MOS-FET model)
.MODEL mynmos NMOS(LEVEL=simple k=2.94e-05 Vth=0.08 rd=.957e7)
.MODEL mypmos PMOS( k=-2.94e-05 Vth=-0.08 rd=.957e7)
M1 Va 3 4 0 mynmos
M2 Vb 0 3 0 mynmos
* nside of the inverter
M3 4 0 Va_and_b 0 mynmos
M4 Va Vdd 4 Vdd mypmos
M5 Vb Vdd 4 Vdd mypmos
* pside of the inverter
M6 4 Vdd Va_and_b Vdd mypmos
V1 Va 0 SIN(0.5 0.5 1 0 0)
V2 Vb 0 SIN(0.5 0.5 2 0.25 0)
V3 Vdd 0 1
.END
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