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Old 10th January 2013, 07:18 PM   #321
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by CeeVee View Post
Thanks Nic,

But...Rdegen trick comes at a price....slightly higher distortion, read this somewhere !, and according to Patrick ( EUVL ) deviating from 5R1 is to be avoided.
I fail to understand this but then that will be because i don't know enough of the subject.

My reasoning was in line with what you just laid out, the lower the Rdegen needed the better i thought. 5R1 being an average value.

I'd love to get the facts on this.
I think the idea of the trick is to lower distortion at the cost of higher local feedback (degeneration).
I am quite sure Patrick picked 5R1 because this is a value that "in average" will yield most NP-matches.
Maybe lower is better, but remember that there is already 11R is series in the F5X.
I think having different Rdeg for each J74 is a DIY'er luxury which can only be recommended
Anyway - wrong thread.
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Old 10th January 2013, 09:27 PM   #322
CeeVee is offline CeeVee  Portugal
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Yep...wrong thread but nice discussion ...see you on the proper one
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Old 10th January 2013, 09:30 PM   #323
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P3 accomplishes similar, correct.
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Old 11th January 2013, 01:53 AM   #324
locky_z is offline locky_z  China
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System the principle of measuring voltage as shown below.Example measure the Vbe,
Click the image to open in full size.
The BE two points of the voltage applied to the ADC input after 91K/12K resistor divider.
If R1/R2 and R3/R4 do not match. R1/R2=91K/12K R3/R4=91.09K/12K
When close sw1, Real Vbe is 0V. But because the resistor no match,The voltage difference between the AD1 and AD2 is

36* (12/(91+12) - 12/(91.09+12))=3.66mV

The system according to the measured, and then multiplied by the coefficient of the resistor divider, and it consider the Vbe voltage is:

3.66mV * (91+12)/12=31.4mV.


So if you measure the JFET Vgs-Id curve, system consider Vgs=0, But in fact the voltage of G/S is not zero.



This error voltage will change with the ground voltage (V) varies.
And when you measure N type ,the Ve is set to 2.5V,and measure the P type,the Ve will set to 36V. So At difference Ve,the error voltage is no same.

So I used some correction algorithm, possible error voltage Ve = 2.5 to 36V range to minimize.
The following diagram is shorted BE and shorted CE,and show Vbe / Vce voltage curve under different Ve.
Click the image to open in full size.
Attached Images
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File Type: png 20090604_52d3d53c250e4ab4d649KUHWZpYR9nz0.png (34.3 KB, 272 views)
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Old 11th January 2013, 09:42 AM   #325
jeepy is offline jeepy  Switzerland
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Quote:
Originally Posted by locky_z View Post
The 2sa970 component foot is right?
Send the save data(.cuv) to me.

When start the measurement, the system control 3 channel output only moment of voltage.
When measure finish, 3 channel output to 0.


If you want to measure 3 channel output voltage by DMM, you can select menu 'option->diagnoosis' and 'Device Test' page -> 'Voltage Test' box,
Set the 3 channel output voltage and click the 'Output' button,
Then you can get the static voltage.
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Old 11th January 2013, 09:45 AM   #326
jeepy is offline jeepy  Switzerland
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I locky-z, thanks for the reply. This is the screen shot for the 2sa970: I alyways get very low hfe I do not not know to send the .cuv file.


Quote:
Originally Posted by locky_z View Post
The 2sa970 component foot is right?
Send the save data(.cuv) to me.

When start the measurement, the system control 3 channel output only moment of voltage.
When measure finish, 3 channel output to 0.


If you want to measure 3 channel output voltage by DMM, you can select menu 'option->diagnoosis' and 'Device Test' page -> 'Voltage Test' box,
Set the 3 channel output voltage and click the 'Output' button,
Then you can get the static voltage.
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Old 11th January 2013, 10:34 AM   #327
jeepy is offline jeepy  Switzerland
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Quote:
Originally Posted by jeepy View Post
I locky-z, thanks for the reply. This is the screen shot for the 2sa970: I alyways get very low hfe I do not not know to send the .cuv file.
The NPN (2sc2240) test seems to be ok!
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Old 11th January 2013, 11:41 AM   #328
locky_z is offline locky_z  China
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2SA970 you need to load the 'PNP Ic-Hfe' condition.
PNP's voltage is negative.
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Old 11th January 2013, 11:56 AM   #329
jeepy is offline jeepy  Switzerland
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Quote:
Originally Posted by locky_z View Post
2SA970 you need to load the 'PNP Ic-Hfe' condition.
PNP's voltage is negative.
It is what I did. I tried 3 different types of PNP transistors with always the same problem: hfe = 2 to 3. Again, The NPN test is OK as you can see on the picture! Could something be wrong with the board? Unfortunately I cannot aford to spend days to fix. Any suggestion will help, thanks
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Old 11th January 2013, 12:19 PM   #330
locky_z is offline locky_z  China
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The PNP measure condition is:
Click the image to open in full size.



But from your picture,I think your condition is NPN type.
Normaly in PNP's result data,The Vce is negative, Ve is +35~36V.
Click the image to open in full size.
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