> I have a small problem with small parts in a small area on a small board
> (so what else is new?).
>
> I have 4 parallel channels of a Quad Transimpedance Amplifier circuit,
> which is very high gain and requires good isolation. The circuit is all
> descrete analog components, mostly 0402, except for the S0-8 op-amps,
> and is packaged quite densely with only .020" between components in the
> tight spots, and no room for package outlines. The circuit is layed out
> very nicely, and is electrically excellent, but unfortunately, there is
> no room for designators.
<snip>
> Anyone out there got any useful ideas?
>
> JaMi Smith

To start off with, this could well be my last post (or else very nearly my
last post) from this email address. I'm currently looking for another job
(preferably in Sydney, Australia, where I am currently living), with my
current job finishing this week (the usual circumstances for this era). But
I have recently signed up to these forums from my home email address, so
other members of these forums will continue to hear from me on an ongoing
basis, but from a different email address.

Now on to this thread.

It is being wise after the event, and not necessarily the "best" way to do
it, but if you want components R1_1, R1_2, R1_3, and R1_4 (say), then add
component R1_1 to the PCB file, then append a "R1" string (on the Top
Overlay layer) to this component (using the Menu item 'Tools/Convert/Add
Selected Primitives to Component'; the component's primitives need to be in
an unlocked state at the time), then create the R1_2, R1_3, and R1_4
components from copying the R1_1 component to the (Protel) clipboard and
then pasting back into the PCB file, then re-annotating the pasted
components as required.

The additional "R1" string is part of each of these components, and will
thus move with its component whenever that component is moved. (Moving the
string *relative* to the component will require the component's primitives
need to be in an unlocked state at the time though, but keep in mind that
the global command feature can be used to unlock (or relock) the primitives
of more than one component at a time.)

All up though, a lot of extra work is called for, even if it is all planned
in advance (to minimise the amount of extra work required). But short of
creating a customised addon Process of some sort (for example, one which
acts upon currently selected "free" strings so that these are automatically
appended to appropriate components which are also currently selected), I am
not sure of any other way of doing it, other than the suggestion made by
others to use the component's Comment strings.

Concerning the use of Comment strings, the Schematic drawings could still be
implemented to display component values (e.g. 10k, 100nF, etc) for each
component by using one of the 16 Part Fields for this purpose, and setting
the corresponding string to be visible. The Part Type (field) (for each
component) could then be used to hold the desired abbreviated Designator
(e.g. "R1" for components R1_1, R1_2, etc), with the corresponding string
set invisible (unless it was desired to keep this visible). When information
was passed from the Schematic File(s) to the PCB file, the Comment string of
each component would then acquire the desired abbreviated Designator for
this, and any subsequent re-synchronisation between the Schematic file(s)
and the PCB file would *not* result in these desired abbreviated Designators
being lost or over-written for *any* of the components (in the PCB file).

Some extra work called for with that method as well, but if planned in
advance, the amount of extra work required could again be reduced (and
probably substantially). If used, I would strongly recommend the addition of
an annotation to the Schematic file(s), documenting the usage of this
technique.

Regards,
Geoff Harland.
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