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Crystal-Controlled Oscillators

Quartz-crystal controlled oscillators17,18 are extensively used in radio, a typical circuit being shown in Fig. 37. The quartz crystal is cut and etched so that it is resonant to the desired frequency. When driven at this frequency by signal feedback through the grid-plate electrode capacitance, the crystal oscillates, produces an output voltage between grid and cathode, this voltage is amplified in the tube, and sustained oscillations result. The equivalent circuit of the quartz crystal and its holder are shown in Fig. 37b.

triode crystal oscillator
Figure 37. Actual and equivalent circuits for a triode crystal oscillator. The C-L circuit should be designed to tune to the crystal frequency, a typical value for C being 100 micromicrofarads. The value of R1 is from 2500 to 25,000 ohms, depending on the grid current that flows, A radio-frequency milliammeter or a radio dial light is often connected in series at point X.


Home Electronic Applications in Communication Oscillators Crystal-Controlled Oscillators

Last Update: 2011-05-27