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Old 26th April 2013, 01:03 AM   #1
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Default BC557 Spice accuracy

I got this model from Onsemi and would like to tweak it to get more realistic gain of around 300, which only shelves off at about 100mA.
This model gives very high gain at low currents, but low gain even at 10mA, although IKF is high

* Model generated on May 13, 05
* MODEL FORMAT: PSpice
.MODEL Qbc557b pnp
+IS=1.68077e-12 BF=3385 NF=1.2121 VAF=196.745
+IKF=1.30809 ISE=1.76095e-13 NE=1.56412 BR=99.5231
+NR=1.23271 VAR=0.978236 IKR=10 ISC=1.76095e-13
+NC=1.21727 RB=17.2944 IRB=0.1 RBM=0.1
+RE=0.354597 RC=1.77298 XTB=0.100946 XTI=1
+EG=1.05 CJE=1.13417e-11 VJE=0.654776 MJE=0.23
+TF=5.99604e-10 XTF=1000 VTF=3935.03 ITF=31.8969
+CJC=9.54039e-12 VJC=0.4 MJC=0.408114 XCJC=0.910091
+FC=0.8 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
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Old 27th April 2013, 01:04 PM   #2
djoffe is offline djoffe  United States
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Bob Cordell's site has spice models that he has tweaked.

http://www.cordellaudio.com/book/Cordell-Models.txt


The BC550C model may be close to what you're looking for.


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Old 27th April 2013, 03:09 PM   #3
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I know the Cordell models, he has done good work reducing the high current gain of power devices to reality
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Old 27th April 2013, 07:05 PM   #4
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by davidsrsb View Post
I got this model from Onsemi and would like to tweak it to get more realistic gain of around 300, which only shelves off at about 100mA.
This model gives very high gain at low currents, but low gain even at 10mA, although IKF is high

* Model generated on May 13, 05
* MODEL FORMAT: PSpice
.MODEL Qbc557b pnp
+IS=1.68077e-12 BF=3385 NF=1.2121 VAF=196.745
+IKF=1.30809 ISE=1.76095e-13 NE=1.56412 BR=99.5231
+NR=1.23271 VAR=0.978236 IKR=10 ISC=1.76095e-13
+NC=1.21727 RB=17.2944 IRB=0.1 RBM=0.1
+RE=0.354597 RC=1.77298 XTB=0.100946 XTI=1
+EG=1.05 CJE=1.13417e-11 VJE=0.654776 MJE=0.23
+TF=5.99604e-10 XTF=1000 VTF=3935.03 ITF=31.8969
+CJC=9.54039e-12 VJC=0.4 MJC=0.408114 XCJC=0.910091
+FC=0.8 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
It looks like BR and BF have a wrongly placed decimal point, that's impossible
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Old 10th May 2013, 02:21 PM   #5
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If you want to tweak it yourself, Bob Cordell's book has a whole chapter on that - I suggest you take a look.

Otherwise you can google for BC557 models. I've done a quick search and found

http://betzler.physik.uni-osnabrueck...pice/uos05.lib

which has more realistic BF/BR values (though I don't know how accurate they are)...

Regards
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Old 11th May 2013, 05:44 PM   #6
Elvee is offline Elvee  Belgium
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The model native to the library of LTspice is quite acceptable, I think it is from Philips.
At low Vce's there are some discrepancies, as is often the case but nothing really catastrophic, like a gain 10x too high
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