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Old 6th November 2011, 03:50 AM   #1
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Location: Malaysia, Selangor
Default LTspice Model incompatible ?

I'm just started to use LTspice as simulator, so I also import some model which I need to use. However, there are some different parameter view between SPICE model and LTspice model. (currently only importing On Semi's model)
There are some parameter that is missing (and many extra) compare to other default device.
Example :
Quote:
Transistor (default, installed with LTspice) :
.model 2N2222 NPN(IS=1E-14 VAF=100
+ BF=200 IKF=0.3 XTB=1.5 BR=3
+ CJC=8E-12 CJE=25E-12 TR=100E-9 TF=400E-12
+ ITF=1 VTF=2 XTF=3 RB=10 RC=.3 RE=.2 Vceo=30 Icrating=800m mfg=Philips)
Transistor (from onsemi website) :
.MODEL Qnjl4281dg_bjt npn
+IS=1.28825e-11 BF=300 NF=1.02019 VAF=10.7547
+IKF=0.97929 ISE=2.28745e-11 NE=1.44568 BR=0.1
+NR=1.29449 VAR=4.22157 IKR=9.7929 ISC=1.04073e-16
+NC=2.85967 RB=1.34764 IRB=0.140361 RBM=0.1
+RE=0.00828762 RC=0.0414381 XTB=0.1 XTI=1
+EG=1.05 CJE=2.34884e-08 VJE=22.295 MJE=0.69263
+TF=1.28186e-09 XTF=131.233 VTF=63578.9 ITF=53.7291
+CJC=4.85466e-10 VJC=0.95 MJC=0.23 XCJC=1
+FC=0.8 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
It was indeed more (alot) information, but lacking some backing information like Vceo, Ic rating, Manufacturer.

below are diode example :
Quote:
Default:
.model 1N914 D(Is=2.52n Rs=.568 N=1.752 Cjo=4p M=.4 tt=20n Iave=200m Vpk=75 mfg=OnSemi type=silicon)

Onsemi :
.MODEL Dnjl4281dg_diode d
+IS=3.44393e-08 RS=0.179036 N=2 EG=1.3
+XTI=2.33354 BV=400 IBV=1e-05 CJO=2.08272e-11
+VJ=1.5 M=0.653713 FC=0.5 TT=5.1937e-08
+KF=0 AF=1
At diode, it is missing Iave(average maximum current), Vpk(peak voltage), manufacturer and Type.
Should we retrieve this information 'manual' by myself from datasheet or it is not important for simulation ? (if you knew the limit)
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Old 6th November 2011, 04:30 AM   #2
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
Those values are just so that LTSpice can show them in it's selection dialog if you add them to your default libraries. If not, dont worry about them.
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Old 10th November 2011, 01:04 PM   #3
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Just to ask, how to simulate an audio amplifier's output to an load (speaker) ?
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Old 10th November 2011, 01:09 PM   #4
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Location: Pretoria
Quote:
Originally Posted by guitar89 View Post
Just to ask, how to simulate an audio amplifier's output to an load (speaker) ?
Simply add an eight ohm resistor to the circuit, between output and ground. It is an over-simplification of an actual speaker load, but does the job.
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Old 10th November 2011, 01:18 PM   #5
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Quote:
Originally Posted by ingenieus View Post
Simply add an eight ohm resistor to the circuit, between output and ground. It is an over-simplification of an actual speaker load, but does the job.
In LTSpice, how to 'show' the result on using the load (simple resistor) on analysis ? (such as transient & AC sweep analysis)
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Old 11th November 2011, 08:08 AM   #6
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Check out the audio amp example that comes with LTspice. It is the file audioamp.asc in the directory C:\Program Files\LTC\LTspiceIV\examples\Educational
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