The relaxation oscillator uses some sort of voltage-breakdown device, such as a neon glow-lamp or unijunction transistor. The feedback oscillator (Fig. 10-1) uses an amplifier circuit and a feedback ...

Most amplifier and oscillator circuits were originally designed during the vacuum-tube era, and they have been converted to transistors and ICs with modifications that relate primarily to the ...

[Qrp-Gaijin] shows how to do it with a single transistor. You can see some videos ... He found that his original oscillator was driving an overtone crystal at its fundamental frequency.

Essentially the whole thing boils down to simply using a transistor to limit the current to the oscillator. A 555 timer is used to pass a triangle wave to the current limiting transistor at ...