On Thu, 17 Jan 2008 11:35:45 -0800, Joerg
wrote:

robb wrote:


I have made some modifications and i have added a schematic image
along with the pcb,


Hmm, first reply went into the weeds.

Still no bypass cap close by. This is not a super-fast opamp but it is
isn't slow enough to go sans cap. C1/C2 are a bit far away. Also,
driving the center of C1/C2 directly can cause some grief. Most opamps
do not like to have a large capacitive load and may oscillate.

Hint: To make your circuits more understandable draw them with the
individual opamp sections separated, not all in one big block. Else
you'll sit there a few years later "What on earth does this part here do?"

Pins 1 and 2 are connected in the layout but not on the schematic ...

More schematic comments:

Perhaps there is a microscopic dot where the wire from pin 2 crosses
the wire from pin 1 to indicate a connection. It is bad practice to
make a 4-way connection like that, as it can easily be confused with a
simple non-connected crossing. It is better to stagger the
connections in one direction so that the connection is obvious.

It is a serious no-no to run wires through components, as you have
done in R5 and R18. C3 is especially bad, as the wire through the cap
looks like the symbol for a feedthrough capacitor which I'm sure is
not what was intended.

As Joerg said, drawing the op-amps using conventional op-amp symbols
rather than as the IC package will make the drawing much more
understandable (and paper is cheap - spread things out a bit.)


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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