1. The problem statement, all variables and given/known data http://img193.imageshack.us/img193/6627/circuitg.jpg [Broken] So I got this circuity thingy and I'm told that each LEDs only lights up at 1.4 V. I am asked what should be the vaue of Vin1 where the green LED lights up. Now, I see I have 2 comparators here. Each one is 15 volts Vcc (either -15 or +15). So, why does the value of Vin1 matter? I just see what's bigger, V+ or V-, and I anyway get 15 volts, so no matter what the LED will light up.