Voltage Status

Dude, did you know you can do the same exact thing with just transistors? By calculating the input voltage of several resistor voltage dividers at multiple increments, say like 1v from 0-5V in your case (so, @ 1V, 2V, 3V, 4V, and 5V) with a minimum output of 0.6-0.75V to bias the transistors. http://everycircuit.com/circuit/5779515151482880

Nice to know, thanks.

But i didn't understand how your Circuit works. (My english is bad)

@isaacsutt you are correct, however, transistors have a much lower open loop gain and will therefore not switch a suddenly as this comparator model. It depends on what the designer is looking for, they may be designing for cost to be as cheap as possible, (they would choose your transistor design) or to have the best performance possible, they may choose this design or a hybrid of the two

Right, of course because a comparator can amplify much smaller changes in voltage, it's going to be much more accurate

@musabe24, that particular circuit basically works by making the first transistor turn on at 1v, the second at 2v, 3rd at 3v, 4th at 4v... and so on, thus turning on each LED as the voltage increases at certain increments. Ok, but how would you control what voltage the transistor's saturate at? ...well, if you know how a diode works, than you also know that it usually has to have at least 0.75V in order to conduct, well a transistor, I'm sure you've heard, is essentially made up of a diode across it's base-emitter junction... Which can lead you to think that it also has a minimum voltage at which it turns on, right? You would be correct. Although for diodes and transistors, this voltage can vary slightly, it's usually always several tenths of a volt, with that being said, if you were to use voltage dividers at the base of each transistor, you can control whatever input voltage you want at the input to give you an approximate output voltage of whatever is required to turn on that transistor (usually about 0.75V). Using this principle, you can have each transistor turn on at 1v higher than the other, to accomplish the same thing you have in your OP AMP circuit here.

Thank you for the description. I can understand your circuit know. Really good idea.

Your welcome!