Cgs synth

--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> A couple of answers -
>
> >I had a few questions, with the two 10n decoupling capacitors do
i
> >just solder them onto the two sets of pads on the back adjacent
to
> >the power connections? and also can someone explain exactly what
> >they do...well i know its for ps decoupling but what exactly does
> >this do or acheive? sorry im still learning, its happening fast
but
> >some of this si still a mystery.
>
> Baically it is a "local power supply" for the circuit in question.
When the
> circuit demands extra power for a split second, it is delivered by
these
> capacitors. These peak power demands cannot be delivered by the
power supply
> itself, due to the resistance of the wires. Note that the
resistances are
> tiny, as are the peak power demands, but without these decoupling
> capacitors, the power lines are dragged around by these peak
demands,
> resulting in noise on the power lines.
>
> Yes, just solder them on the pads on the back of the PCB.
>
>
> >Where I am lost is i kind of assummed that if the icon for the
> >transistor on the PCB shows an arrow pointing out of the device
that
> >that indicated the emmitter and if it had an arrow pointing into
the
> >devide that indicated the collector but i've done some web
browsing
> >and have found sites suggesting that a PNP is shown with an arrow
> >pointing into the device for the emmitor and that an NPN uses an
> >outward pointing arrow for the emmitter???? guess im trying to
get
> >this right.
>
> Correct. It essentially represents the diode that is the base-
emitter junction.
>
> >Ken kindly taught me how to test transistors with my multi meter
(ok
> >im very new at this) so with that i was able to determine that
one
> >of the transistors was a NPN and the other a PNP and what was the
> >emitter etc but now im not sure which way they should have gone
into
> >the board......with my thinking i put the 2n3904 with the emitter
> >connected to the pad with the arrow pointing out of the device
and
> >with the 2n3906 i soldered the connector to the pad with the
arrow
> >pointing into the device. I think this may be where i went wrong
as
> >from my research the icons are reversed depending on if its a PNP
or
> >NPN so i think i ahve one in the wrong way :(
>
> Emmitters fo the the arrow symbols, yes. The little half-circle
that is
> drawn around the transistor symbol on the PCB actually indicates
in which
> way the package should be installed.
>
> Ken
>
_____________________________________________________________________
__
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
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