Reply to thread

This is not a useful circuit for a summer and needs Thevenin conversions to make sense.

The "voltage summer"  must be inverting as shown already. But you get to choose the Vref point for Vin+ to add to the inverted inputs.  That means for positive only inputs and single + supply, you define Vcc/2 as your virtual gnd = Vin+ if you want.

Then the output must feedback to make both inputs matching for a "virtual null" where both inputs match and equal Vcc/2. instead of 0V.

[ATTACH=full]198047[/ATTACH]

So guess how you make it non-inverting?