[sdiy] prototype boarding (help?) and homemade pcbs.

[René Schmitz]

Hi James,

James Dunn wrote:
> 
> On 13 May 2006, at 13:50, Seb Francis wrote:
> 
>> And, as for unreliable .. I've never had any problems (aside from
>> the obvious parasitic capacitance...
> 
> 
> How big an issue is this for stripboard? What precautions can be
> taken to avoid it? Is it only an issue for super-sensitive circuits?

As usual it depends. Its an issue with impedances high enough so that
the roll off of the parasitic lowpasses plays a significant role.
This happens seldomly in audio circuits. (And indeed I had the opposite
case too: a circuit that was stable on SBB but not on perfboard, because
the circuit needed a little capacitance...)
Or a node has such a high impedance that the capacitive pickup from
adjacent signals can become visible. I.e. small signals are more prone
to pickup than large ones.
You need to be aware of parasitic capacitance/coupling (and inductance)
on perfboard and PCBs anyway.
And there are cures for both problems. Rearranging the circuit so that
the signal that is picked up is moved away from the high Z nodes. E.g.
move it one row apart, and ground the row in the middle. Keep high
impedance nodes short, and if possible reduce the impedance.
So the standard rule applies: You can do anything, if done right. :-)

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159