Posted on Jan 22, 2013

Diagram shows a 50MHz oscillator operating on a third harmonic. The collector`s load resistor R1 has been increased because the quartz crystal`s internal series resistance Rs increases with frequency in the VHF range. The crystal`s internal series resistance Rs is 30ohm, and the transistor`s minimum current gain HFI, is 100.

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Using the same technique as for the 20 MHz oscillator, the external series RLCL equivalent load seen by the 50MHz crystal is 5.6ohm (RL) and 1000pF (CL).

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