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.

Precision Phase Shift (CB5440E)
We find this circuit in a 1980s documentation. The integrated ones are of the time and their...
Gain 1000 Sample and Hold (CB5960E)
This 80's circuit has been winning. It is a 1 000 gain sample and hold circuit and an offset...
Bridge type transistor tester (CB20526E)
We found this circuit in documentation from the 1950s. The circuit basically applies to germanium...