This very low power amplifier is designed by Amperex for hearing aids. It is based on TAA370 which is not an integrated circuit that can be found today.
This Philips circuit of the 70's makes use of components of the time. The DZD40 is an uncommon...
This circuit suggested by Motorola can be used as LED high frequency modulator. One possible...
Suggested by General Electric in a 1965 documentation, this circuit can use the TIC106 as an SCR....