CRYSTAL_CONTROLLED_REFLECTION_OSCILLATOR

Published:2009/7/7 7:25:00 Author:May | From:SeekIC

This unit is easily tunable and stable, consumes little power, and costs less than other types of oscillators that operate at the same frequencies. This unusual combination of features is made possible by a design concept that includes operation of the transistor well beyond the 3 dB frequency of its current-versus-frequency curve. The concept takes advantage of newly available crystals that resonate at frequencies up to about 1 GHz. The emitter of transistor Q is connected with variable capacitor C1 and series-resonant crystal X.The emitter is also connected to ground through bias resistor R1. The base is connected to the parallel combination of inductor L and capacitor C3 through dc-blocking capacitor and C4 and is forward biased with respect to the emitter by resistors R3 and R4. Impedance Z could be the 220-Ω resistor shown or any small impedance that enables the extraction of the output signal through coupling capacitor C2. If Z is a tuned circuit, it is tuned to the frequency of the crystal.



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