Basically, I need to monitor a circuit's output so I can activate another system. The output voltage of active stage is 140mV.
If I am not wrong (from what I read about transistors) 140mV is not enough to put a BJT transistor into saturation (ON mode).
The end goal is turning on an LED and/or a relay, so I really need transistor in the saturation region.
I don't want to use a micro-controller's ADC to measure the voltage for such simple device (cost wise)
How can solve the problem in a simplest manner possible?