I'm trying to build a simple circuit to detect when a lamp (tail light) is burned out, and light an LED in the dash. I think I can use a couple op amps but not sure how. My plan was to connect non-inv input to the (-) lead of the lamp socket and the other input to chassis ground. But I think this is the opposite of what I want. When the bulb burns out no current runs through it to the input line so it should be nearly the same as input 2. But this will result in linear mode and I want positive saturation to power the LED. If anybody can guide me in the right direction I would appreciate it.