When your Microcontroller project, RF transceiver circuit, or FM radio requires external 1 to 20 MHz oscillators then this is the circuit I bet will need for your project.

This circuit is simple to implement and parts can be obtained easily and at low cost. It requires a battery of 5 to 12 Vdc, it also work at lower voltage levels. Lower voltage levels can be experimental. I had this circuit work for me at actually down to 1.8 Vdc after manipulating the feedback caps (82 pf connected to the base of transistor and 0.001 uF connected between the 82 pF and ground.) Also low voltage operation may or may not work for certain crystal frequencies.

 Notes about this circuit:

1. Xrystals value may range from 1 MHz to 20 MHz.
2. Output frequency followes crystal XTAL frequency.
3. Circuit works for fundamental xtal frequency operation only.
4. Preferred crystal capacitance is 32 pF. Otherwise output frequency may slightly deviate.
5. Most bipolar transistors would work such as 2N3904 or 2N2222 as long as transistor is frequency capable.
6. When using PNP transistor reverse battery polarity.
7. caps 82 pf connected to the base of transistor and 0.001 uF connected between the 82 pF and ground preferred to be NPO ceramic disk.
8. For accurate output frequency use variable 50 pF across the XTAL and/or exchange the 0.001 uF cap connected to the XTAL with variable cap.
9. 0.001 uF cap connected to emitter of transistor is blocking cap.
10. Low cost, simple, and small size.
11. Output can be buffered with op amp and amplified. This can make nice wireless transmitter.
12. For different output frequency change XTAL value. See note 8 above to fine tune frequency if needed.

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