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.
This configuration is very traditional, appearing in several publications around the world. This...
This is the normal configuration for dividing a TTL signal by 7. The 7490 can divide by other...
Found in a 1967 Electronics World, this oscillator changes its tone when objects move in their...