This circuit was found in a 90’s Electronic Engineering. The signal is sinusoidal with the frequency given by the non-value components that form the resonant network.
This configuration that appears several times with variations on this site is from old American...
This configuration (somewhat critical, as the imbalance of characteristics between transformers can cause...
This circuit is from a Popular Electronics of the 90's. Any power MOSFET can be used. The circuit...