- #36
jim hardy
Science Advisor
Gold Member
Dearly Missed
- 9,832
- 4,895
Rudinhoob said:I thought it's 0 it it's considered a reference node. This is how it's treated in circuit books, they show the non-inverting input for an inverting OpAmp configuration connected to a common node, using the "ground" symbol, and the same symbol used for the input voltage source's negative rail.
In your left hand circuit you connected +input to a definite point, the power supply centertap.
In your right hand one you didn't, you left it to find its own level.
Simply calling it "reference" doesn't make the rest of the circuit respect it.
In the boooks, they don't usually show the power supply. Power supply is used to define 'circuit common' , usually power supply centertap.
For opamps like LM324 which is designed to operate with single supply, they often but not always use power supply negative instead.
I strongly recommend you look into the first article in that Analog Devices link posted by dlgoff.
It was written before op-amp fundamentals became so entrenched we forgot how to teach them. Too many cooks and all that...
old jim