Found in Linear Technology documentation, this circuit drains only 70 uA of the monitored circuit. The components used are from that time.
This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the...
This circuit turns on your car's backlight when a vehicle coming from behind gets too close to it...
Using the 7805 circuit as equivalent, we can obtain 5 V with current up to 1 A. This circuit is...