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M.E. Brinson: Faculty of Computing, London Metropolitan University, UK; Qucs development team: mbrin72043@yahoo.co.uk

S. Jahn: Qucs project manager, Munich, Germany; stefan@lkcc.org

Presented on April 2, 2009, at the COMON meeting, IHP, Frankfurt (Oder), Germany 1

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Qucs is an open source circuit simulator with a graphical user interface (GUI)

based on QTby TrolltechQucs is available from http://qucs.sourceforge.net/

Qucs aims to support a wide range of circuit simulation, including DC, AC,transient, S-parameter, noise analysis, Harmonic Balance analysis and digital

system simulation

Developed using GNU/Linux under the General Public License (GPL)

Available for most of the popular computer operating systems, including

GNU/Linux, Windows, Solaris, NetBSD, FreeBSD and MacOS

Qucs is one of the GPL circuit simulators taking part in the MOS-AK Verilog-A

standardization initiativeDevelopers: Loose group of international engineers, scientists and programmersQucs is multilingual and has been translated into: Romanian, German

Italian, Polish, French, Portuguese, Spanish, Japanese, Hungarian, Hebrew,

Swedish, Turkish, Russian, Czech and Catalan

2

http://qucs.sourceforge.net/http://qucs.sourceforge.net/

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Start Qucs by issuing the command

OR by clicking the appropriate icon on your start menu or desktop

3

Open projects

folders

File -> Application

settings

Schematic circuit drawing

window

Drawing tool bar

Drop-down menus

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4

the GUI:used to create schematics, setup simulations, display simulation results

and writing VHDL/Verilog code amongst other tasksthe analogue simulator: a command line program which is run by the GUI

to simulate user generated schematicsa simple text editor: which is used to display netlists, simulation log files and to edit

SPICE, Touchstone and other text filesa filter synthesis program: used for the design of passive filtersa transmission line calculator: used for the design and analysis of transmission linesa component libraryan attenuator synthesis program: used for the design of passive attenuatorsa command line conversion program: this program acts as a tool for the import and

export of data sets, netlists and schematics from and to other CAD/EDA software

The GUI is also used by Qucs to launch other EDA tools:FreeHDL(http://www.freehdl.seul.org)

for digital VHDL, Icurus Verilog( http://icarus.com/eda/verilog/) for digital Verilog and

ASCO( http://asco.sourceforge.net/) for circuit optimization

http://www.freehdl.seul.org/http://icarus.com/eda/verilog/http://asco.sourceforge.net/http://asco.sourceforge.net/http://icarus.com/eda/verilog/http://www.freehdl.seul.org/

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Either press the button above the projects folder or use the menu entry

and enter the project name

Confirm the dialog by pressing button. Qucs then opens the Phototransistor

project and displays a blank project window with the tab open.

5

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Non-linear components Verilog-A components

File components

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Simulations Diagrams

Cartesian Polar TabularSmith Chart Admittance Smith

Polar-Smith Combi

Smith-Polar Combi

3D-Cartesian

Locus curve

Timing Diagram

Truth Table

Paintings

Line Arrow Text

Ellipse Rectangle

filled Ellipse

filled Rectangle

Elliptic Arc

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Generation of circuits using Qucs design tool suite:

passive filter synthesis example

Low pass filter

synthesis

13

Other synthesis/design tools:

Text Editor, Line Calculator, Matching Circuits and Attenuator Synthesis

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http://www.gnu.org/software/octave/http://www.mathworks.com/

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The phototransistorconsists of an Ebers-Moll

bipolar junction transistor

model which has been

extended to include

depletion and diffusion

capacitance, forward and

reverse Early effects,

high current forward and

reverse beta degradation,

thermal and shot noise,

plus a light bus which

connects external light

signals to the

phototransistor

Light bus

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Name Symbol Description Unit Default

BF f Forward beta 100

BR r Reverse beta 0.1

Is Is Saturation current A 1e-10

Nf Nf Forward emission coefficient 1

Nr Nr Reverse emission coefficient 1

Var Var Reverse Early voltage V 100

Vaf Vaf Forward Early voltage V 100

Mje Mje Base-emitter exponential factor 0.33

Vje Vje Base-emitter built-in potential V 0.75

Cje Cje Base-emitter zero-bias depletion capacitance F 1p

Mjc Mjc Base-collector exponential factor 0.33

Vjc Vjc Base-collector built-in potential V 0.75

Cjc Cjc Base-colector zero-bias depletion capacitance F 1pTr Tr Ideal reverse transit time s 100n

Tf Tf Ideal forward transit time s 0.1n

Ikf Ikf High current corner for forward beta A 0.5

Ikr Ikr High current corner for reverse beta A 0.5

Rc Rc Collector series resistance 2

Re Re Emitter series resistance 1

Rb Rb Base series resistance 100

Kf Kf Flicker noise coefficient 1e-12

Ffe Ffe Flicker noise frequency exponent 1

Af Af Flicker noise exponent 1

Responsivity Responsivity Responsivity at peak wavelength A/W 1.5

P0 P0 Relative selectivity polynomial coefficient % 2.6122x103

P1 P1 Relative selectivity polynomial coefficient %/nm -1.4893x101

P2 P2 Relative selectivity polynomial coefficient %/nm2 3.0332x10-2

P3 P3 Relative selectivity polynomial coefficient %/nm3 -2.5708x10-5

P4 P4 Relative selectivity polynomial coefficient %/nm4 7.6923x10-917

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IEC=Is[exp VBI , CINrvt 300 1]ICC=Is[exp VBI , EINfvt 300 1 ]

IDC2=IEC

r GMINVBI , CI IDE2=

ICC

f GMINVBI , EI

ICT= [ICCIEC ]

q1

2

114q2

q1=1VBI , CI

Vaf

VBI , EIVar

q2=ICCIkf

IECIkr

DC I/V characteristics

CBC=dQ BI , CIdVBI , CI

= Cjc

[1VBI , CIVjc ]Mjc

Tr dIEC

dVBI , CI VBI , CI Vjc

2

=2MjcCjc[2MjcVBI , CIVjc 1Mjc ]Tr dIECdVBI , CI VBI , CI >=Vjc2CBE= dQ BI , EIdVBI , EI= Cje[1VBI , EIVje ]

MjeTr dICCdVBI , EI VBI , EI Vje2

=2MjeCje[2MjeVBI , EIVje 1Mje ] Tr dICCdVBI , EI+ VBI , EI >= Vje2

Capacitance {

{

Iopt=Gpbcopt Gpbc=Re!"e#s$t$v$t%Respo#s$v$t%

f100

Re !"e#s$t$v$t%=&1'2'2

('3

)'4

$*c#2=4+T

*c f $Re#2=

4+T

Ref

$*ba#2=8+T

*b f $*bb#2=

8+T

*b f $bs#

2=2qIBf $bf#2=+f

IB-f

f.fef

Photo current {

Noise {

vt T=+Tq

Where K is the Boltzmann constant, T is the temperature in Kelvin, q is the electron charge, GMIN is a small

admittance in parallel with the device junctions, f is the noise frequency bandwidth in Hz and is the lightwavelength in nm. Other symbols and node names are defined in the previous slides.

$ICTs#2=2qICf

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I=IV ,/=dI

dVQ=Q I ,V

C=dQ

dV=dQ V

dV

dQ I

dI /

Equation defined device Large signal DC model Generate symbol

Redrawn symbol

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Charge equations

Q BI , CI = 0

VBI ,CI

CBCdV =TrIEC2MjcCjc[MjcVBI , CI

2

Vjc 1Mjc VBI , CI ] VBI , CI Vjc2

=TrIECCjcVjc

1Mjc[1

{1

VBI , CIVjc }

1Mjc

] V BI , CI

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AC gain Cbe and Rbe extraction

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Si phototransistor relative

sensitivity data

Curve fitting programMeasured data

*e!"e#s$t$v$t%=01223

34

4

01ere0=2.6122e3,1=1.4893e1,2=3.0332e-2,3=2.5708e-5,4=7.69e-9

EDD light

bus model

Iopt=*e!"e#s$t$v$t%*espo#s$v$t%po2erf100

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24

Phototransistor output

characteristicsPhototransistor responsivity

characteristics

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Qucs noise voltage source

V"D f=3

acfe

Where VPSD(f)is the voltage spectral

density at frequency f in V2/ Hz, U is

the voltage spectral density asf goes

to zero, a, cand eare coefficients that

determine the type of noise generated;

white and shot noise with U=1, e=0,

c=1 and a=0, and flicker noise with

U=Kf, e=Ffe, c=1 and a=0.

Noise parametersNote: Resistor thermal noise

is automatically generated by Qucs

$bs#=2qIB -/45

$bf#=+f

-f

f.fe-/45

$ICTs#=2qIC -/45

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26

Variable light power Variable wavelength

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Model

27

Store in Qucs

library

Generate Verilog-A

code

Use Create Library from Project menu

`include "disciplines.vams"`include "constants.vams"module phototransistor (Collector, Base, Emitter, Power, Wavelength);inout Collector, Base, Emitter, Power, Wavelength;electrical Collector, Base, Emitter, Power, Wavelength; Definition of internal local nodeselectrical C!, B!, B!, E!; Parameter values and description text`de#ine attr(t$t) (%t$t%)parameter real B#&' #rom '*in#+ attr(in#o&"#orward eta");

parameter real Br&.' #rom 'e-*in#+ `attr(in#o&"reverse eta"); *parameter real P/&-.012e-0 #rom-in#*in#+

`attr(in#o&"relative selectivit3 pol3nomial coe##icient" );parameter real P4&1.5/e-5 #rom-in#*in#+

`attr(in#o&"relative selectivit3 pol3nomial coe##icient" ); Definition of internal variables and quantitiesreal 67, con', con, con/, con4, con0, con, con1, con2, con5, con', 7wo8, 9our:7,', >, !B, !C, !E, 8', ?el@ensitivit3; 8uantitiesanalog egin Module initialisation codeA(initialmodel) egin 67 & `P:%/`P8; con'&'(=#%67); con&'(=r%67); con/&'-

9our:7&4%`P:%Dtemperature; 9our:7 & 4%:%7 end; Model quantity equations and current contributions !CC&!s%(lime$p(6(B!,E!)%con')-'); !EC&!s%(lime$p(6(B!,C!)%con)-');>'&'6(B!,C!)6a# 6(B!,E!)6ar; >&(!CC!F#) (!EC!Fr); !B&6(B!,B!)%con2;

!C&6(Collector,C!)%con5; !E&6(E!,Emitter)%con'; !(Collector,C!) G !C; !(Base,B!) G 6(Base, B!)%con2; !(B!, B!) G !B; !(E!, Emitter) G !E; !(B!,C!) G (!ECBr) ))); 8'&(6(B!,C!) H6c) I 7r%!ECCc%con%(

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Compile phototransitor.vafile

with ADMS*using

1. admsXml phototransistor.va -e qucsVersion.xml -e qucsMODULEcore.xml

: generates files phototransistor.core.cppand phototransistor.core.h

2. admsXml phototransistor.va -e qucsVersiom.xml -e qucsMODULEdefs.xml

: generates file phototransistor.defs.h

3. admsXml phototransistor.va -e qucsVersion.xml -e qucsMODULEgui.xml

: generates files phototransistor.gui.cppphototransistor.gui.h

4. admsXml phototransistor.va -e analogfunction.xml

: generates files phototransistor.analogfunction.cpp andphototransistor. analogfunction.h

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* L. Lemaitre and B. Gu, ADMS-a fully customizable Verilog-AMS compiler approach, 2006.

Available from http://www.mos-ak.org/montreux/posters/17_Lemaitre_MOS-AK06.pdf.

S. Jahn and H. Parruitte, Qucs: A description, Verilog-AMS interface, 2006. Available from: http://qucs.sourceforge.net/docs.html.

http://www.mos-ak.org/montreux/posters/17_Lemaitre_MOS-AK06.pdfhttp://www.mos-ak.org/montreux/posters/17_Lemaitre_MOS-AK06.pdfhttp://qucs.sourceforge.net/docs.htmlhttp://qucs.sourceforge.net/docs.htmlhttp://www.mos-ak.org/montreux/posters/17_Lemaitre_MOS-AK06.pdf

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Editing phototransistor.cpp continued

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Symbol data

for

schematic

capture

Symbol outline

Port connections

Coordinates

marking area of box

surrounding symbol

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phototransistor.png

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FINAL STEP Compile qucs and qucs-coreRun qucs and test new

phototransistor model

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1. Qucs is a freely available circuit simulator distributed as open source software

under the GNU/Linux General Public Licence (GPL).

2. This demonstration has attempted to outline the fundamental features of the package,

its available components, libraries, built-in design aids, and analysis types.

3. The demonstration also introduces a number of basic approaches to circuit simulation

using Qucs.

4. The presentation also showed how the compact semiconductor modeling and

circuit macromodeling features implemented in the current Qucs release can be

used to develop equation-defined component models of established and emerging

technology devices.

5. The latter sections of the demonstration concentrated on using ADMS to compile

Verilog-A compact device models and the steps needed to link such models

with the main body of the Qucs C++ code.