On Oct 5, 2009, at 01:55, Andrew Scheidler wrote:
The main difference I've found with 2N3904s (apart from reversed
pinout) is that BC547C's have higher HFe gains of around 400, rather
than the 250-ish of a 2N3904.
The only time this made a difference for me was in an analogue noise
circuit, where the 2N3904 with the chosen components was not producing
enough gain to drive a sample and hold to give around ±5V output. A
regular BC547B had only a little higher output, so a BC547C was used
and did the trick. FWIW, it was in a modded EFM LFO5A.
That's probably a rare case though.....
Cheers,
Dave
> I was told (years ago) that I could just use 3904 transistors and putSame here.
> them in backwards. The 3904 is easy to find and I've had no problems
> with this substitution...
The main difference I've found with 2N3904s (apart from reversed
pinout) is that BC547C's have higher HFe gains of around 400, rather
than the 250-ish of a 2N3904.
The only time this made a difference for me was in an analogue noise
circuit, where the 2N3904 with the chosen components was not producing
enough gain to drive a sample and hold to give around ±5V output. A
regular BC547B had only a little higher output, so a BC547C was used
and did the trick. FWIW, it was in a modded EFM LFO5A.
That's probably a rare case though.....
Cheers,
Dave
> Drew
>
>
> To: cgs_synth@yahoogroups.com
> From: sasami@...
> Date: Sun, 4 Oct 2009 18:35:56 +1100
> Subject: Re: [cgs_synth] CGS31: sub BC549 for the BC547?
>
> BC547 is "generic". I've used all sorts of NPN transistors in
> locations that
> I label as BC547. So, short answer, the substitution is fine.
> Ken
>
> >would it be a bad idea to substitute the BC549 for the BC547 called
> for in
> the digital noise circuit? thanks!
> >
> >
> >
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