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Old 16th June 2012, 02:15 AM   #241
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HI locky_z,

If you are still selling your tracer on taobao, please let me have the link to it. Thank you.

regards
BP
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Old 16th June 2012, 02:37 AM   #242
locky_z is offline locky_z  China
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It seem that the system try to keep 'Vce' fixed,but do not well.
The system keep Vce fixed is use software feedback.

Example measure p type, VCE fix at 15V and Vgs step up to 2.6V.
The process step is:
1.System will set E channel output 36V,B output 36-2.6=33.4V
2.System set C channel output 36-15=21V,
3.Measure the Vce, example Vce is 0.5V,
4.Compare the measure Vce(0.5V) and VCE(15V), The difference is -14.5V,so system adjust the C channel output to 21+(-14.5)=6.5V,
5.Measure the Vce again,and adjust C channel output
6.Until 10 loops or Vce-VCE less 50mV.

At step 4,5 ,system increase the C channel output, and the current also grow, and the VE may change, so It may reduce a little adjust.may make system hard to keep Vce fixed.
And you use LT1013 replace LM358,Its gain is better than LM358,It keep VE stabel better than LM358.

You change the parameter 'Options->Config->Voltage drop(Source)' to 3V, and try again,

Or

Try to load 'Vgs-Id(No Fix Vce)' . This measure condition is Set C channel to max output voltage, It mean Vrc(the voltage drop of RC) + Vce is fixed. It no longer adjust Vce,the curve may more smooth.
But the Vce of every point on curve is difference.
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Old 7th July 2012, 05:49 AM   #243
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I think I have a problem mesuring HFe for BC327 40 and BC337 40

HFe range for those is up to 630
The transistors are from Fairchild direct so no fakes

The PNP I have tried so far all mesure HFe much larger than transistor specification
of the first 100 measured are all above HFe 600 and up to 720

Can msure of PNP mesure be out of calibration?
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Old 7th July 2012, 06:24 AM   #244
locky_z is offline locky_z  China
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Each hfe-Ic curve at the beginning part, is not accurate enough.
Because the current is very small, The voltage drop on the RC RB is small, System measure them not accurate. So Hfe=Ic/Ib is vary greatly.

From the data,you can get the IC and Ib , and you use Vrc=Ic*RC,Vrb=Ib*RB to calculate VRC,VRB.
If Vrc & Vrb is samll than 0.25V,means they may not accurate enough. I suggest discard them.
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Old 7th July 2012, 02:48 PM   #245
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Tanks locky_z
I have set up
mesure form 0.5v to 10 0.5 step fixed VCE 10 V current max 800 mA
all NPN mesure in range all PNP are 60 or more over spec
Ofset on PNP does not make sense
When I mesure with Atlas component tester mesure is different and PNP are ok
If not acurate it is ok as long as this is constant
Will try to post curves later
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Old 9th July 2012, 11:56 AM   #246
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Here are curve from BC337-40 NPN and BC327-40 PNP
PNP mesure is wrong, very hi HFE
Transistors are original Fairchild from manufacturer
I have mesured 400 PNP and 1000 NPN

NPN ok PNP vrong go up to 770 big offset

I don't understand why?

When I mesure with Atlas component tester PNP HFe is ok and same as NPN
Attached Images
File Type: jpg BC327-40 curve.JPG (355.7 KB, 296 views)
File Type: jpg BC337-40 curve.JPG (558.0 KB, 263 views)
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Old 9th July 2012, 12:40 PM   #247
locky_z is offline locky_z  China
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When Ic is less 0.5mA,The Ib is less than 0.5mA/Hfe=0.5/700=700nA,
The buffer(OP07) bias current is 1.2nA,offset current is 0.5nA, they all less than the Ib, So the system measure the Ib is right,
So I think the pnp curve is right. Its Hfe is more than 700.


I look at your picture,The Ic is less 1.8mA, I suggest use RC=12K,
When ic less 0.5mA, the Vrc=0.5*12K=6V,
If you use RC=1K, the Vrc only 0.5*1K=0.5V,
System measure the small voltage may have less 15mV error.So if use RC=12K is better than RC=1K
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Old 9th July 2012, 06:13 PM   #248
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Tanks locky I will try with 12 K still PNP mesure different from NPN.
Error shuld be same if there is error.

When I mesure with different instrument HFe is as on data sheet.

Data sheet say HFe is between 400 and 630 for both transistors
Many NPN mesure at around 520
PNP around 640 if I change formulae to Hfe=abs(Ic/Ib)-120 then HFe is ok
I do not understand why ?
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Old 10th July 2012, 12:35 AM   #249
locky_z is offline locky_z  China
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You can adjust the measure condition ,and make the IC range about 1~20mA,and look at their hfe range.
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Old 10th July 2012, 12:11 PM   #250
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Ok locky_z

I am thinking that maybe there is sometink wrong with polarity inverse circuit for PNP circuit
Can you mark SCH for where to look
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