This is another of the circuits with the LM380 that we have in this section. We found it in an article about Walkman amplifiers in the Radio Electronics magazine of March 1986.
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...
This interesting source or isolation transformer also allows to vary the output voltage by...
In this circuit the CA3140, an operational amplifier, is used as a comparator with the zener diode...