[Help-gnucap] Re: Help-gnucap Digest, Vol 48, Issue 11

[Jesus Genicio]

El dom, 31-08-2008 a las 12:00 -0400, address@hidden
escribió:
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> Today's Topics:
> 
>    1. Re: Model for led diode (Thaddeus Meizelis)
>    2. diodes - determining IS. (al davis)
>    3. Re: Model for led diode (al davis)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 29 Aug 2008 11:34:21 -0500
> From: "Thaddeus Meizelis" <address@hidden>
> Subject: Re: [Help-gnucap] Model for led diode
> To: address@hidden
> Message-ID:
>       <address@hidden>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> FWIW, Here is a model of an LED I found on a messageboard somewhere:
> 
> Typ RED,GREEN,YELLOW,AMBER GaAs LED:
> Vf=2.1V Vr=4V If=40mA trr=3uS
> 
> .MODEL LED2 D (IS=93.1P RS=42M N=4.61 BV=4 IBV=10U
> + CJO=2.97P VJ=.75 M=.333 TT=4.32U)
> 
> Please forgive me, I did not record the source for this diode.
> 
> Hope this helps.
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Sat, 30 Aug 2008 23:25:36 -0400
> From: al davis <address@hidden>
> Subject: [Help-gnucap] diodes - determining IS.
> To: address@hidden
> Message-ID: <address@hidden>
> Content-Type: Text/Plain;  charset="iso-8859-1"
> 
> Here's a way to find the saturation current of a diode.
> (repost from gEDA-user)
> 
> 
> FAQ......
> >  Where can I find some instructions on obtaining and adding
> > new models?
> 
> As you probably already figured out, you need "model" statement 
> to parameterize the diode ...
> 
> D2 (a k) 1n4004
> 
> Now you need a model statement ...
> 
> .model 1n4004 d (a whole bunch of parameters)
> 
> You could do a web search for a detailed model, but usually you 
> can just do some experimenting..   
> 
> If you are at the stage where you are asking about this, the 
> detail will only confuse you, most likely of the worst kind of 
> confusion, where you don't realize it.
> 
> Most of the time, the only parameter you need for a diode is 
> saturation current, which of course isn't in the data sheet.
> 
> ok .. so how do I figure that out??
> 
> Well ...  Look at the specs, or measure it.  Let's say we found 
> that the forward voltage at 1 amp is .7 volts.  
> 
> Use the simulator to build a test circuit ..
> 
> I1 (0 1) dc 1
> D1 (1 0) my_diode
> 
> You need a model statement ..
> .model my_diode d (is=something)
> 
> but I don't know what the value of something is.
> 
> With gnucap .. try this.......
> 
> gnucap> build
> >i1 (0 1) dc 1
> >d1 (1 0) my_diode
> >.model my_diode d is=something
> >                   ******** blank line to exit build mode
> gnucap> probe  op  v(1)
> parameter something has no value
> gnucap> op
> #           v(1)      
>  27.        0.83376                    **** using default IS
> gnucap> param something=1u
> gnucap> op
> #           v(1)      
>  27.        0.35733   
> gnucap> param something=1n
> gnucap> op
> #           v(1)      
>  27.        0.53599   
> gnucap> param something=1p
> gnucap> op
> #           v(1)      
>  27.        0.71465   
> gnucap> param something=2p
> gnucap> op
> #           v(1)      
>  27.        0.69673   
> gnucap> param something=1.5p
> gnucap> op
> #           v(1)      
>  27.        0.70417   
> gnucap> param something=1.8p
> gnucap> op
> #           v(1)      
>  27.        0.69945   
> gnucap> param something=1.7p
> gnucap> op
> #           v(1)      
>  27.        0.70093   
> gnucap> param something=1.75p
> gnucap> op
> #           v(1)      
>  27.        0.70018   
> gnucap> exit
> 
> 
> There ..  close enough ,,,  
> Now use the value 1.75p for IS.
> 
> Here's your model statement:
> .model my_diode d is=1.75p
> 
> 
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Sun, 31 Aug 2008 03:31:18 -0400
> From: al davis <address@hidden>
> Subject: Re: [Help-gnucap] Model for led diode
> To: address@hidden
> Message-ID: <address@hidden>
> Content-Type: text/plain;  charset="us-ascii"
> 
> On Thursday 28 August 2008, Jesus Genicio wrote:
> > Vcc ( 1 0 )  DC  5.
> > Vin ( 5 0 ) PULSE iv= 0. pv= 5. delay= 1. rise= 0. fall= 0.
> > width= 2. period= 4.
> > Rc ( 1 8 )  122.
> > Rb ( 5 2 )  12.K
> > Rled ( 8 3 )  121.
> > Q1 ( 3 2 0 )  Q2N2219A  area= 1.
> >
> > The result is correct:
> >
> > gnucap> tran 0 2 0.1
> > #Time       V(5)       V(1)       V(Rled)
> >.........
> >  1.3        5.         5.         2.4256
> 
> > Rled must be one led.
> >
> > If i change Rled for a diode 1N4004, example. The results is
> >
> > gnucap> tran 0 2 0.1
> > #Time       V(5)       V(1)       V(D1)
> >.............
> >  1.3        5.         5.         0.74569
> >  1.4        5.         5.         0.74569
> >  1.5        5.         5.         0.74569
> >  1.6        5.         5.         0.74569
> >  1.7        5.         5.         0.74569
> >  1.8        5.         5.         0.74569
> >  1.9        5.         5.         0.74569
> >  2.         5.         5.         0.74569
> >
> > But V(D1) must be 2.42 for light diode. If change Rc, de
> > V(D1) is equal but vce change...
> 
> That result is correct for a 1N4004.
> 
> The key parameter is "IS" (saturation current).  To make a model 
> for your LED, make a ".model" where you specify only "IS".  
> Choose the value so you get the correct forward voltage.
> 
> 
> 
> 
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> 
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> 
> End of Help-gnucap Digest, Vol 48, Issue 11
> *******************************************

Thanks to all:

I make the change in "is" and ok, the diode led run in 2.46 volts with 5
volts in Vin but de vce with vin=0 is only the 2.8 volst.....

gnucap> list

Vcc ( 1 0 )  DC  5.
Vin ( 5 0 ) PULSE iv= 0. pv= 5. delay= 1. rise= 1. fall= 1. width= 2.
period= 5.
Rc ( 1 8 )  250.
Rb ( 5 2 )  25.K
Q1 ( 3 2 0 )  QBSR14  area= 1.
.model  Led  d  (  tnom= 27.  is= 1.E-45  rs=NA( 0.)  n=NA( 1.)
tt=NA( 0.)  cjo=NA( 0.)  pb=NA( 1.)  mj=NA( 0.5)  egap=NA( 1.11)
xti=NA( 3.)  fc=NA( 0.5))
*+()
.model  QBSR14  npn  (level=1  kf= 0.  af= 1.  bf= 256.7  br= 6.59  is=
29.13f  nf= 0.9926  nr= 0.9844  vaf= 80.99  var= 101.2  isc= 320.3p
c4=NA( 0.)  nc=NA( 2.)  ise=NA( 0.)  c2=NA( 0.)  ne=NA( 1.5)  rb=NA( 0.)
rbm=NA( 0.)  re=NA( 0.)  rc=NA( 0.)  cjc=NA( 0.)  cje=NA( 0.)
cjs=NA( 0.)  fc=NA( 0.5)  mjc=NA( 0.33)  mje=NA( 0.33)  mjs=NA( 0.)
vjc=NA( 0.75)  vje=NA( 0.75)  vjs=NA( 0.75)  xcjc=NA( 1.)  itf=NA( 0.)
ptf=NA( 0.)  tf=NA( 0.)  tr=NA( 0.)  xtf=NA( 0.)  xtb=NA( 0.)
xti=NA( 3.)  eg=NA( 1.11))
*+()
*
D1 ( 8 3 )  Led  area= 1.
.model  Q2N2219A  npn  (level=1  kf= 0.  af= 1.  bf=NA( 100.)
br=NA( 1.)  is=NA( 100.E-18)  nf=NA( 1.)  nr=NA( 1.)  isc=NA( 0.)
c4=NA( 0.)  nc=NA( 2.)  ise=NA( 0.)  c2=NA( 0.)  ne=NA( 1.5)  ikr= 0.285
rb= 1.53  rbm=NA( 1.53)  re= 0.383  rc= 0.153  cjc= 20.2p  cje= 24.1p
cjs=NA( 0.)  fc=NA( 0.5)  mjc= 0.3  mje= 0.5  mjs=NA( 0.)  vjc= 0.3
vje= 1.1  vjs=NA( 0.75)  xcjc=NA( 1.)  itf=NA( 0.)  ptf=NA( 0.)  tf=
454.p  tr= 315.n  xtf=NA( 0.)  xtb= 1.5  xti=NA( 3.)  eg=NA( 1.11))
*+()
gnucap> print tran v(vin) v(d1) v(rc) vce(q1)

gnucap> tran 0 5 0.2

#Time       v(Vin)     v(D1)      v(Rc)      vce(Q1)
 0.         3.2074f    2.1327     163.09n    2.8673
 0.2        3.2074f    2.1327     163.09n    2.8673
 0.4        3.2074f    2.1327     163.09n    2.8673
 0.6        3.2074f    2.1327     163.09n    2.8673
 0.8        3.2074f    2.1327     163.09n    2.8673
 1.         3.2074f    2.1327     163.09n    2.8673
 1.2        1.         2.5341     0.88932    1.5766
 1.4        2.         2.5587     2.297      0.14439
 1.6        3.         2.5591     2.3374     0.10353
 1.8        4.         2.5593     2.3532     0.087548
 2.         5.         2.5594     2.3628     0.077836
 2.2        5.         2.5594     2.3628     0.077836
 2.4        5.         2.5594     2.3628     0.077836
 2.6        5.         2.5594     2.3628     0.077836
 2.8        5.         2.5594     2.3628     0.077836
 3.         5.         2.5594     2.3628     0.077836
 3.2        5.         2.5594     2.3628     0.077836
 3.4        5.         2.5594     2.3628     0.077836
 3.6        5.         2.5594     2.3628     0.077836
 3.8        5.         2.5594     2.3628     0.077836
 4.         5.         2.5594     2.3628     0.077836
 4.2        4.         2.5593     2.3532     0.087548
 4.4        3.         2.5591     2.3374     0.10353
 4.6        2.         2.5587     2.297      0.14439
 4.8        1.         2.5341     0.88932    1.5766
 5.         3.2074f    2.1327     163.09n    2.8673

Vin=0 => Led off but v(d1)=2.13 Volts and led light. Sorry, the "is" ok
but there are some parameter more that configure to make that diode run
correctly?.

One reply is that " you need more study of theory of circuits" :)),
please be pacient. Thanks.

I "googling",  but the search is very poor. The models that i'm found
don't  is very correct, or i'm think that no, because the v(d1) when
v(vin) is zero is about of 2.1 volt, this is incorrect. vin=0 vce=vcc.?

the only way that i found for this, is:

vin=0, V(d1)=2.13 but ic=163nA and this is off.?

I'm Sorry, thanks and one Regards :))