We found this circuit in a technical documentation for the National Semiconductor LM3909. The circuit consists of a low consumption continuity tester powered by a single battery.
This series LED circuit was found in the February 1992 issue of Radio Electronics magazine. The...
We found this circuit in the Linear Applications Handbook by National Semiconductor. The circuit uses...
The noise comes from the PN junction of a common silicon diode. Since no gain is given by the...