Thanks for reply everyone, well, right now it is a scope as I am trying to see what's really going on with signal and understand mechanisms behind the scene, difference between different wiring etc. Right now it is the oscilloscope and as a voltmeter I do understand that it has "infinite" resistance so it's not sinking any current thus not consuming power, that I understand now after first replies. I will be experimenting more, jsut ordered few different opamps from digikey, will break them out and start playing, but just thinking out loud more in that direction, let's say you have some kind if DAC in the output, like arduino for example, even in analogRead mode pin can sink current, right? So obviously then it will use some power? Can you limit power consumption by simply adding resistor? Please don't forget I'm a beginner so I can get some things totally wrong in such case don't kick me too hard 