[time-nuts] HP 105B Modification
Gerhard Hoffmann
dk4xp at hoffmann-hochfrequenz.de
Wed Dec 9 20:27:08 UTC 2009
On Wed, 09 Dec 2009 15:08:15 +1300, you wrote:
>Another point is the LTSpice LED model isn't particularly accurate for
>simulating the effects of temperature variations.
>Does anyone knows of more accurate LTSpice compatible LED models?
>
>The LED model voltage drop increases with temperature even at low
>current, whilst the voltage drop across a real LED at low currents
>decreases with temperature.
>In practice the variation in the LED forward drop tracks the variation
>in the pnp Vbe quite well.
I have used this model and also this diode:
* from OSRAM TOPLED library
*
*
.MODEL LH_T676_typ D
+ IS=5.5621E-24
+ N=1.3448
+ RS=4.3842
+ IKF=17.186E-3
Comparing the current with a BC860 PNP and a 15 Ohm emitter resistor
worked quite nicely, so I had no reason to investigate the model.
(as you wrote, too)
I also tried to operate a power LED with the base bias divider current
of all 6 distribution channels combined(70 mA tot.) to recycle the current
but it seemed that the power LED had more Ohmic resistance than
6 times LHT676. Could be just my sample, and it was close to the max. specs.
Gerhard
More information about the time-nuts
mailing list