fet low distortion crystal oscillator

Posted on Feb 6, 2014

This is a design circuit for Low Distortion Crystal Oscillator circuit. This circuit generate a sine wave that has low phase noise and distortion. This circuit can be used to perform a crystal with less than 1mV dissipated in crystal. The crystal is used to filter the signal current. This is the figure of the circuit; If the impedance loads is low

fet low distortion crystal oscillator
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, the JFET will drive the impedance. When the loads is about 50ohm, it will better if an emitter follower combined with a voltage step-down transformer or matching network for further buffering. The value of C3 determined the output voltage, if the lower output voltage is required, the C3 ²s value should be increased and decrease the value of C3 when the larger output voltage is needed. If overtone crystal is used, a choke should replace the 1K emitter resistor. This choke must be resonates with C2 at a frequency slightly above the fundamental frequency for thirdovertonecrystals. When uses the high-Q overtone crystal, the value of C3 should be lower because the High-Qovertonecrystals should be driven at much lower levels than fundamental crystals. Besides that, the output level should be set as low as possible. If the crystal`srated power or current is known, the drive level can be measured. To measure drive level temporarily connect a 100 ohm across C3 and measure the signal level on the source of the FET. The crystal current is determined by V/100.

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