Found in a 1969 EEE, this circuit is based on an operational amplifier of the time and on old type MOSFETs. The components support modern equivalents.
This circuit was obtained from a 1990s documentation. The transistor admits equivalent and other...
The circuit shown is an amplifier for medium impedance headphones including bass and treble...
This signal follower is from a 1970's documentation. So it uses the traditional configuration at the time...