This circuit was found in Siliconix documentation from the 1980s. Equivalent operational amplifiers can be used and the output current is very low.
With this luminous remote control, which we found in a 1990 publication, using a flashlight you...
We found this circuit in a 1967 Electronics World. The circuit can be designed to control other...
This circuit can be used in a signal level indicator with LEDs. The circuit is from an Electronics Now...