[sdiy] Using BC847S in exponential converter

[Gerard]

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 Lots of VCO designs are using outdated (well, hard to obtain) matched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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