Optical sensor for PC (CB20548E)

This circuit was found in a PC documentation from 1996. It can be used as a shield with modern microcontrollers.

Instrumentation Amplifier TL082 (CB901E)
This very high input impedance circuit is suggested by Texas Instruments. The circuit can be...
Cascading the 4017 (CB211)
Here we show how two 4017s can be cascaded to count above 10. The circuits are driven by a square...
Small Transistor Amplifier (CB1370E)
This small power amplifier makes use of an output transformer given its design time. In fact, the...