On Fri, 15 Apr 2005 12:06:03 GMT, Lancer wrote in
g4fv515va9hcfooqrnoqd3gfdpm6jvv2te@2355323778:

On Fri, 15 Apr 2005 03:32:29 -0700, Frank Gilliland
wrote:

On Fri, 15 Apr 2005 03:28:01 -0700, Frank Gilliland
wrote in
:

snip
....... ground the NC end of VR1....


Correction: tie the NC end of VR1 to the center rail.




Why would you want the inverting input of A2 tied to DC potential?

When you adjust VR1 won't you be setting the DC output level of A2?


The center rail (the "6.2 VDC bus") is a virtual ground. Fixing the
inverting input of A2 to this level prevents DC drift and/or lockup of
A2. For the other op-amps, the addition of a 1 Meg resistor from the
inverting input to this virtual ground provides the same protection.

I may not have explained that very well......





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