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Old 10th May 2004, 08:14 PM   #1
bengt is offline bengt  Sweden
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Default Diod bap811

Hi !

Can anyone tell me what i can replace D101,D102 with. The number is Bap811 and I have tried to find about it but failur. Is it possible to replace with 1N4148 ???


bengt
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Old 10th May 2004, 09:13 PM   #2
dhaen is offline dhaen  Europe
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As you can see from the attached image (in Polish I think), this is a stabiliser diode with much greater voltage drop than a 1n4148. There must be more common types available today. If not, you could try 3 1n4148's in series.
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Old 10th May 2004, 09:17 PM   #3
bengt is offline bengt  Sweden
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Great !!!

I have search the internet for several days without finding any data for this Bap811 diode.
This is in a preamp and I will try to take 3 or four 1N4148 instead

Thanks for your fast reply !!!



cheers !!!


Bengt
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Old 10th May 2004, 09:19 PM   #4
dhaen is offline dhaen  Europe
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Maybe 3 is closer. I had edited my reply while you posted.
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Old 10th May 2004, 09:40 PM   #5
mandat is offline mandat  Poland
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BAP811 was produced in UNITRA CEMI (Poland) a few years ago; Zener diode in TO-92 case
IF: 0,05A, Tjmax: 150C, Uz: 1.45-1.65V IR: 1uA for UR: 6V
It means that you can replaced it by 2 ordinary, low power silicon diodes, like 1N4148, coupled in series or even two CE junctions of low power transistors connected in the same manner e.g. BCxxx.
obudowa: TO-92
The link below leads you to a catalogue but in polish language.
http://www.eres.w3.alpha.pl/index1.php?text=25
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Old 10th May 2004, 09:54 PM   #6
mandat is offline mandat  Poland
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erratum
BE junctions
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Old 10th May 2004, 10:43 PM   #7
bengt is offline bengt  Sweden
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So, this was the only thing left for testing my preamp and I tried with two 1N4148 for each Bap811 and it seems to work well.

But Mandat, you wrote that it is a zener diod. Is it possible to take just one zenerdiode with 3.1 volt instead of this two Bap811 ? just curious.....

Anyway, it seems to work well, thanks to you people here !!!!


Thanks,

Bengt
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Old 10th May 2004, 11:03 PM   #8
Eva is offline Eva  Spain
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Changing the number of 1N4148 allows to select the operation mode of the output stage

With two 1N4148 it will work in class B, with three 1N4148 it would work in class AB and with more diodes it will work in class A. The optimun number of diodes depends on the load impedance and the supply voltage

The original design appears to work in class AB with 1 to 2mA biasing. I would recomend using at least four diodes or a Vbe multiplier [an additional BC550C/BC560C and two resistors]. A zener may be also suitable
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Old 10th May 2004, 11:32 PM   #9
mandat is offline mandat  Poland
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I think that two BAP811 (stabilising diode) should not be replaced by one Zener diode (3.1 or 3.3 V) because these devices have different temperature coefficient, and some problems with preamp stability could arise.
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Old 11th May 2004, 12:52 AM   #10
Eva is offline Eva  Spain
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With 330ohm emitter resistors, even a drift of 1 volt between 'hot' and 'cold' would cause a mere 1.47mA drift in bias current. Not a problem, I think. I would use 5mA bias [or even 10mA also reducing emitter resistors to 100-150 ohms]
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