White LED Spice Model
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From: Jim Thompson on 28 Jan 2010 09:24 On Wed, 27 Jan 2010 21:49:23 -0700, "Paul Hovnanian P.E." <Paul(a)Hovnanian.com> wrote: >Jon Kirwan wrote: >> >> On Wed, 27 Jan 2010 19:28:57 -0700, "Paul Hovnanian P.E." >> <Paul(a)Hovnanian.com> wrote: >> >> >I found my old HP-41C curve fit program card. Then I found my old >> >HP-41C. >> > >> >The model I get from your curve is: >> > >> >.MODEL MyWhiteLED D >> >+ IS = 4.4249E-9 >> >+ N = 8.3923 >> >+ RS = 7.7980 >> > >> >No subcircuits required. >> >> That N looks frightening. > >Yes, but it seems to work for the white LED (probably a blue LED) curve. >I haven't gotten into the physics of the problem, but the emmission >coefficient (N) seems to track the band gap of the junction involved. So >this isn't as bizarre as it appears. Here's a white LED Spice model that I created by fitting to data points of a real device: ****************************************************************** **** My White LED **** ..SUBCKT MyWhiteLED A K D_D1 N_1 0 D1N4148 F_F1 N_3 K VF_F1 1 VF_F1 N_2 N_1 0V E_E1 N_2 0 N_3 K 0.228 R_R1 A N_3 5 ..ENDS MyWhiteLED ****************************************************************** Retrieve the original posting at... Newsgroups: alt.binaries.schematics.electronic Subject: White LED Spice Model Date: Fri, 15 Jan 2010 09:18:31 -0700 Message-ID: <qo41l5llt9mtna5bepi6facrf03p4p7l7s(a)4ax.com> X-Newsreader: Forte Agent 6.00/32.1186 to see simulation versus data points. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 28 Jan 2010 09:59 On Wed, 27 Jan 2010 19:28:57 -0700, "Paul Hovnanian P.E." <Paul(a)Hovnanian.com> wrote: >I found my old HP-41C curve fit program card. Then I found my old >HP-41C. > >The model I get from your curve is: > >.MODEL MyWhiteLED D >+ IS = 4.4249E-9 >+ N = 8.3923 >+ RS = 7.7980 > >No subcircuits required. I'm not sure if that will work over temperature. It would be interesting if someone could take data at several different temperatures. It'll be tricky, you have to be quick or self-heating will screw up the result. Maybe with a plotting curve tracer? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 28 Jan 2010 10:15 On Wed, 27 Jan 2010 19:28:57 -0700, "Paul Hovnanian P.E." <Paul(a)Hovnanian.com> wrote: >I found my old HP-41C curve fit program card. Then I found my old >HP-41C. > >The model I get from your curve is: > >.MODEL MyWhiteLED D >+ IS = 4.4249E-9 >+ N = 8.3923 >+ RS = 7.7980 > >No subcircuits required. BTW: "your curve"? Whose curve? You clip too much, Paul. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Paul Hovnanian P.E. on 28 Jan 2010 13:26 Jim Thompson wrote: > On Wed, 27 Jan 2010 19:28:57 -0700, "Paul Hovnanian P.E." > <Paul(a)Hovnanian.com> wrote: > >>I found my old HP-41C curve fit program card. Then I found my old >>HP-41C. >> >>The model I get from your curve is: >> >>.MODEL MyWhiteLED D >>+ IS = 4.4249E-9 >>+ N = 8.3923 >>+ RS = 7.7980 >> >>No subcircuits required. > > I'm not sure if that will work over temperature. > > It would be interesting if someone could take data at several > different temperatures. It'll be tricky, you have to be quick or > self-heating will screw up the result. Maybe with a plotting curve > tracer? That's a good point. N is often used as a 'fudge factor' for Vt, so for wild values of N (greater than 2.0 or less than 1.0) it would be reasonable to expect that nVt may vary with temp (or other conditions) in some different manner than kT/q. Where I've seen weird values of N pop up, SPICE started to fall apart for anything other then approximate values. It was time to toss the standard model and go with something cooked up by the physicists. -- Paul Hovnanian paul(a)hovnanian.com ---------------------------------------------------------------------- Have gnu, will travel.
From: Paul Hovnanian P.E. on 28 Jan 2010 13:36
Jim Thompson wrote: > On Wed, 27 Jan 2010 19:28:57 -0700, "Paul Hovnanian P.E." > <Paul(a)Hovnanian.com> wrote: > >>I found my old HP-41C curve fit program card. Then I found my old >>HP-41C. >> >>The model I get from your curve is: >> >>.MODEL MyWhiteLED D >>+ IS = 4.4249E-9 >>+ N = 8.3923 >>+ RS = 7.7980 >> >>No subcircuits required. > > BTW: "your curve"? Whose curve? You clip too much, Paul. Sorry. I took your spice model from your post, ran it for 70 current points and poked every tenth one into my program. I didn't have the table function values (the PDF you posted in a.b.s.e which I assume were your original measured data points). By the way, there appears to be an outlying data point in your graph. So I was actually curve fitting to your curve fit. -- Paul Hovnanian paul(a)hovnanian.com ---------------------------------------------------------------------- Have gnu, will travel. |