Transistor sine-wave LC oscillators. Some general considerations and new developments

The paper begins by showing that various well-known simple oscillator circuits, usually analysed separately, are essentially equivalent to one another if certain reasonable assumptions are made, and appreciation of this fact simplifies the design problem. A discussion follows concerning class-C oscillators and the difficulty of combining high efficiency with a satisfactory degree of independence of transistor parameters. The problem of avoiding squegging is also considered. A simple push-pull high-efficiency oscillator is then described, in which substantially constant current flows in each transistor for the whole of its 180° conduction angle. This oscillator is believed to possess a unique combination of desirable features. Another unusual high-efficiency oscillator is then presented, which is more elaborate than the previous one but which has advantages in certain respects. The paper ends with a description of an oscillator based on the `long-tailed-pair¿ circuit. The oscillator is exceptionally easy to design and make, and is suitable for applications where high efficiency is not important. It can supply either a sine wave or a square wave, or both.