[sdiy] Using BC847S in exponential converter

[Stewart Pye]

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 Lots of VCO designs are using outdated (well, hard to obtain) matched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