[sdiy] Using BC847S in exponential converter

[Neil Johnson]

Hi,

Stewart Pye wrote:
> 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.
>
> 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 Lots of VCO designs are using outdated (well, hard to obtain) matched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

Or look in the earlier synth diy archives at retrosynth.com ( http:// 
search.retrosynth.com/synth-diy/index.html ) and you'll find my  
posting from April 2001:

http://search.retrosynth.com/synth-diy/search/lookit.cgi?-v0104.488

with the following response from Philips:

"If you want any form of matching we can offer BC847BS with gain  
matching
to B gain group. Basically it is two BC847B die."

Cheers,
Neil
--
http://www.njohnson.co.uk