active filter tuned oscillator
Active Filter necessary consists of an Active element like an OP-Amp FET, BJT Voltage/Current Amplifier in it. Strict definition of an Active Component is the one that changes the input waveform to the component. In other words all elements that can store energy can be vaguely classified as Active Elements.
Now Tuned Oscillators are the elements that employ the +ve feedback. Adhering to the "Barkhasan Criteria" Avβ = 1 and total loop phase shift = 180°. And thus acting as a sine-wave generator. Anyway they are called "Tuned" as they have capacitive/inductive elements that from the feedback path that tune the oscillator to the frequency.
Example Hartley Oscillator, colpitts oscillators.
~Kalyan.