Bilateral current source 2 (CB20819E)

We found this circuit in an American publication from the 1980s. Equivalent modern operational amplifiers can be used.

AC to DC converter (CB16696E)
This circuit was found in a 1992 publication, using an operational amplifier not very common...
Earphone Amplifier (CB416)
This is a amplifier for XTAL high impedance earphones or piezoelectric types. Current drain is...
Relay Shield LM111 (CB20168E)
This circuit is from the LM111 manual of the 1980s. The component no longer exists, but...