SPICE on transistors
The following is a chart showing what my simulator shows for mje-15032 audio power transistor. I measured at 4 different Vce, 5, 20, 35 and 55. Does this chart look reasonable to you? Especially the variation of hFE based not on Ic but on Vce?
PS: I could go downstairs and test the real thing but it is too cold to get out :-)
At Vce=75V hFE shows as 265 at 100mA which can't be right either. The SPICE model came straight from ON.
The circuit I use looks like this (perhaps I have screwed up somehow):
PS: the model
* Model Generated by MODPEX *
*Copyright(c) Symmetry Design Systems*
* All Rights Reserved *
* UNPUBLISHED LICENSED SOFTWARE *
* Contains Proprietary Information *
* Which is The Property of *
* SYMMETRY OR ITS LICENSORS *
* Modeling services provided by *
* Interface Technologies www.i-t.com *
.MODEL Qmje15032 npn
+IS=3.7344e-10 BF=86.8313 NF=1.23974 VAF=31.5491
+IKF=9.1678 ISE=9.2499e-12 NE=3.28127 BR=5.59346
+NR=1.33161 VAR=2.1791 IKR=5.15023 ISC=4e-13
+NC=4 RB=9.54492 IRB=0.1 RBM=0.1
+RE=0.000568481 RC=0.0931741 XTB=0.737036 XTI=1.04983
+EG=1.206 CJE=3.05969e-09 VJE=0.648491 MJE=0.352663
+TF=4.94819e-09 XTF=1.50001 VTF=1.0001 ITF=0.999982
+CJC=3.00108e-10 VJC=0.600021 MJC=0.40991 XCJC=0.8
+FC=0.534651 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
* Model generated on Feb 1, 2004
* Model format: PSpice
i ve got the same figure for 75V VCE..
that seems right..
Can't be right. I think I shall brave the cold and try to test it out for real.
This is the BC548C. Again it looks dead wrong. hfE cannot double at the same Ic simply because Vce has increased. Or can it?
I can't speak for the DC accuracy of most ONSemi models, which usually match the datasheet poorly, except in special cases of "featured" transistors like the BD787/788, and even then I wonder.
I think this is an issue of model quality, not a problem with SPICE.
Parametr VAF isn't correct. Substitute aproximately VAF = 100
Measure the two points with a real transistor Ib = 1mA, Uce = 10V and 30V
figure Ice - Vce
figure h parameter - Vce
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SPICE model index 20503 entries in this list.
Model produced equivalent elements, the model does not match the datasheet. When production is different, the model does not correspond exactly. Datasheet sets the limit values, datasheet does not give a picture of the current production. In the model, we can not leave the smallest parameter value and also to write the greatest value of the parameter. In the model we need to write a specific value.
This "discovery" helps me understand a little bit better how transistors work. For example from the Toshiba datasheet Danhard posted, there is a graph in there showing great hFE variation based on Vce, but am still not sure I understand the meaning.
I will now go and try on a couple of transistors, I will record the data and plot new real graphs, not simulated. Let's see what I get.
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