| Re: Buffer for my system? [message #75504 is a reply to message #75501] |
Tue, 12 February 2013 10:45   |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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Good advice: I think the gist of what you're saying is correct, and would limit fan-out to a reasonable number of connections.
The thing that concerns me more than drive level is noise immunity, and that having a bunch of unbalanced lines connected together might introduce more noise. If the source output impedance is really low, like 25Ω, then the source/sink will probably do a pretty good job of swamping any noise. Even the typical range of 50Ω to 100Ω outputs are probably fine. But if the output impedance is on the high side, say 250Ω, then it can't do as good a job of clamping the line and noise is potentially more likely. So I guess my real concern with fan-out isn't the drive level but the vulnerability to noise.
As to buffer amps, I think they're good for the noise problem (if one finds they have it) but I wouldn't put one in just to do it. If there is no noise problem, don't. No need to introduce anything into the signal path that isn't necessary.
Boils down to a situation where you just have to see what you have and decide what to do. If you don't have a noise and/or drive problem, don't add a buffer stage.
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