[sdiy] Using Opamps as INV or NON-INV amplifiers

[Ian Fritz]

At 11:51 AM 6/21/2006, Dave Kendall wrote:
>Apart from the gain being minimum of 1 for a non-inverting amp, are there
>any other advantages or gotchas about using one form or another? There's
>lots of stuff about op-amps out there, but I'm still a bit unsure about the
>practical differences in use. It would seem that a single NON INV amp is
>easier to implement, and yet often the INV configuration is used, with a
>second re-inverting stage ...

Dave --

That's a real good question.  The INV configuration is often used just for 
convenience.  You can sum several signals independently with it (no 
interaction between the signals), so it is simple.  However, often it is 
used where the design could be done more effectively with the NON INV 
configuration.

At one point I worked out the equations for the general  case of arbitrary 
inputs to both INV and NON, and they are quite useful once you learn how 
they work.  You can see some typical applications in the writeup for my 
MIDI wind controller.

One more thing ... you can use the NON configuration for gain less than one 
-- just use a voltage divider attenuator at the input.  :-)

   Ian

   http://home.earthlink.net/~ijfritz/sos_circ.htm