The circuit shown is from Texas Instruments optoelectronics documentation. The input signal is audio and equivalent LEDs can be used. Other operational amplifiers can also be used.
We found this circuit in a Motorola manual. The circuit employs operationals that are uncommon today...
In the figure we have the way to use a voltage comparator powered by a voltage to control a...
CTS IoT Quartz Crystals Available through Mouser Electronics, CTS quartz crystals are especially suited...