Cross-coupled LC oscillator

A cross-coupled LC oscillator is a type of electronic oscillator that employs a pair of cross-coupled electronic active devices—typically metal-oxide-semiconductor field-effect transistors (MOSFETs) or bipolar junction transistors (BJTs)—and a resonant LC filter, commonly referred to as a tank, which stores and exchanges energy between the inductor and the capacitor. The cross-coupled devices act as a differential transconductor to compensate for losses in the LC network and sustain autonomous oscillation.

Source: Wikipedia — Cross-coupled LC oscillator (CC BY-SA 4.0)