Radio with amplifier (CB20486E)

We found this circuit in a publication of 1991. The audio amplifier is an operational that admits equivalent.

Transformer Audio Output Stage (CB18304E)
This circuit with only one transistor was found in Japanese documentation from the 1960s. The...
ADC buffer (CB9313E)
This circuit was found in documentation from Analog Devices from the 90s. The circuit uses...
Optical isolator (CB8272E)
This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit...