[sdiy] Using BC847S in exponential converter

[Stewart Pye]

OK, my mistake. The BC847 is a single transistor while the BC847S is 
dual, however the BCM847BS may have better matching as they specify it 
on the datasheet, unlike the BC847S.

http://www.datasheet4u.com/html/B/C/M/BCM847_PhilipsSemiconductors.pdf.html

Regards,
Stewart.

Gerard wrote:
> Hi,
>
> Well this is the one I ordered: 
> http://www.produktinfo.conrad.com/datenblaetter/150000-174999/153224-da-01-en-AF_Transistor_BC847S.pdf 
>
> which is a double transistor, but as mentioned by Samppa it is not a 
> monolithic design (apparently), but at least the datasheet mentions 
> that the transistor have "high matching", and I assume that the 
> thermal coupling will also be high (given the incredible small size of 
> the package), at least better than glueing two devices together.
>
> Regards, Gerard
>
>
> Stewart Pye schreef:
>> Hi Gerard,
>>
>> I'm guessing you mean BCM847. The BC847 is a single transistor. I 
>> haven't tried them yet but I am going to get some to try out. From 
>> what I remember from the datasheet the matching is not quite as good 
>> as some of the other matched pairs we're used to seeing, but not too 
>> bad.
>>
>> They might be good for ladder filter and diff amps too, and the 
>> BCM857 PNP version could be used for the ARP4072 filter and other 
>> circuits where you require a PNP pair.
>>
>> Cheers,
>> Stewart.
>>
>>
>> Gerard wrote:
>>> Lots of VCO designs are using outdated (well, hard to obtain) matched
>>> transistor pairs like the LM394 and MAT02 in their exponential 
>>> converter.
>>> Has anyone on the list ever tried the BC847S that can be found real 
>>> cheap
>>> (I bought 100 of them for 5€ at Conrad) in such an application?
>>>
>>> The only reference on the list I could find was this post:
>>> http://dropmix.xs4all.nl/pipermail/synth-diy/2008-August/008924.html
>>>
>>> I'll do some experiments anyway :)
>>>
>>> Regards, Gerard
>>>
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>>>   
>>
>
>