on Pot (dejavu)

[KLEIN_B at a1.wdc.com]

(This was supposed to go out before my last post but my
glorious email system caused it to choke.....)

You CAN use the pot in the feedback of the op amp.  Just tie the wiper
of the pot to the appropriate END of the pot travel.  That way if it
opens due to wiper action it opens to the max. gain set by the value
of the pot.  You wouldn't need the feedback resistor then.  Like:


 -----------/\/\/\/\/\/\-x-------
                 ^       |
                 |-------|

Twist the 2 wires leading from the pcb to the pot together so any
noise pickup is common-mode and reduced.  Place a small cap (50-100p)from
"-" input to output of the opamp (right at the op amp leads).  This
will tend to prevent oscillations.  Keep the leads to the pot away
from any high-level signal paths as if you open the pot up for high
gain you will be more susceptable to interference and oscillations.

klein_b at a1.wdc.com