This is the basic configuration of an operational amplifier sample & hold circuit. The FET and transistor are commonly used. The circuit is from an 80's documentation.
This traditional triplier configuration with the 555 can be found in other articles on the...
This transistorized oscillator, a modification of the Colpitts oscillator, was found in the...
This circuit is from 1995 documentation. The power depends on the transformer, which in this case...