The most simple LTSpice LED simulation question

Thread Starter

Lucky-Luka

Joined Mar 28, 2019
165
Hi all
I just wanted to simulate a 5mm green LED connected to a DC source.
I expected to see more than 2V at the A point of the circuit but it looks like it's more or less 0.7V which is the typical forward voltage of a diode.
Where i am going wrong?
Thanks
 

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k1ng 1337

Joined Sep 11, 2020
413
Give falstad.com/circuit/ simulator a try if you haven't already. I like how many of the examples can be used as templates for your own circuits and it's GUI is a lot easier than spice if your having some trouble.
 

ericgibbs

Joined Jan 29, 2010
15,332
hi dl,
The N parameter for LED's is higher than that for regular Diodes.
Clip from LTS standard.dio folder.

eg;
.MODEL LedRed D (IS=93.2P RS=42M N=3.73 BV=4 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=4 type=LED)
.MODEL LedGreen D (IS=93.2P RS=42M N=4.61 EG=4 BV=4 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=4 type=LED)
.MODEL LedBLUE D (IS=93.2P RS=42M N=7.47 BV=5 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=5 type=LED)
.model LedWHITE D(Is=0.27n Rs=5.65 N=6.79 Cjo=42p Iave=30m Vpk=5 type=LED)
.model BLUE D(Is=25e-14 N=5 Rs=14 Eg=2.23 Tnom=27deg type=LED)
.model GREEN D(Is=1e-19 N=2 Rs=1.5 Eg=2.23 Tnom=27deg type=LED)
.model RED D(Is=1.0p N=3 Rs=9 Eg=2.17 Tnom=27deg type=LED)
 

eetech00

Joined Jun 8, 2013
3,087
hi dl,
The N parameter for LED's is higher than that for regular Diodes.
Clip from LTS standard.dio folder.

eg;
.MODEL LedRed D (IS=93.2P RS=42M N=3.73 BV=4 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=4 type=LED)
.MODEL LedGreen D (IS=93.2P RS=42M N=4.61 EG=4 BV=4 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=4 type=LED)
.MODEL LedBLUE D (IS=93.2P RS=42M N=7.47 BV=5 IBV=10U CJO=2.97P VJ=.75 M=.333 TT=4.32U Iave=40m Vpk=5 type=LED)
.model LedWHITE D(Is=0.27n Rs=5.65 N=6.79 Cjo=42p Iave=30m Vpk=5 type=LED)
.model BLUE D(Is=25e-14 N=5 Rs=14 Eg=2.23 Tnom=27deg type=LED)
.model GREEN D(Is=1e-19 N=2 Rs=1.5 Eg=2.23 Tnom=27deg type=LED)
.model RED D(Is=1.0p N=3 Rs=9 Eg=2.17 Tnom=27deg type=LED)
There is no LEDs like that in the standard.dio distribution.
You must have added them.
 

eetech00

Joined Jun 8, 2013
3,087
Hi all
I just wanted to simulate a 5mm green LED connected to a DC source.
I expected to see more than 2V at the A point of the circuit but it looks like it's more or less 0.7V which is the typical forward voltage of a diode.
Where i am going wrong?
Thanks
Try this LED L200TGB5:
* Hi-Eff Green, GAP/GAP
.Model L200TG5B D(IS=1.69111e-008 N=5.23202 RS=11.3667 CJO=53p BV=5.0 IBV=100u IAVE=30m mfg=LEDTRONICS type=LED)

Its a better LED model.

1640821228464.png

1640821287675.png
 
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