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Re: [Help-gnucap] Model for led diode
From: |
al davis |
Subject: |
Re: [Help-gnucap] Model for led diode |
Date: |
Sun, 31 Aug 2008 03:31:18 -0400 |
User-agent: |
KMail/1.9.9 |
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.