How is positive feedback supplied in a Colpitts oscillator?

A Colpitts oscillator is easily identified by its use of two capacitors in series across an inductor to form its tuned tank circuit. The connection between these two capacitors acts as a capacitive voltage divider. This divider taps off a specific portion of the oscillating signal and routes it back to the active device to provide the positive feedback needed to sustain oscillation. By contrast, a Hartley oscillator relies on a tapped coil (an inductive divider) for its feedback. Link coupling is a method for transferring power between circuits, and a neutralizing capacitor is used to prevent unwanted oscillations in amplifiers, not to sustain them. A helpful mnemonic is to associate the "C" in Colpitts with "Capacitive" divider.