[sdiy] Circuit / Op-amp question

[mirwin at qouest.net]

Tim,
A good time to use duals instead of quads is when low offset voltage is 
required for precision work - most duals are more tightly spec'd than 
the equivalent quad version.

There is a spec for amplifier-amplifier isolation on most datasheets for 
duals and quads - usually on the order of (-)110 to 120 dB, measured at 
a particular frequency. 

Using quads instead of duals can sometimes simplify the layout.... I'd 
rather put extra time into a layout and use quads. Texas Instruments 
even has/had octal versions of the common BIFET op amps.

For some applications (eg. phase shifters) I  implemented the  input 
buffer, summing stage, regen amp and output stage using one TL074 with 
good results. Might not want a triangle LFO to share the same chip with 
a high-gain preamp though.
Regards, Mike