27_MHz_AND_49_MHz_RE_OSCILLATOR_TRANSMITTER

Published:2009/6/30 3:00:00 Author:May | From:SeekIC

The modulator and oscillator consist of two NPN transistors. The base of the modulator transistor is driven by a bidirectional current source with the voltage range for the high condition limited by a saturating PNP collector to the pin 4 VREG voltage and low condition limited by a saturating NPN collector in series with a diode to ground. The crystal oscillator/transmi tter transistor is configured to oscillate in a class C mode. Because third overtone crystals are used for 27 MHz or 49 MHz applications a tuned collector load must be used to guarantee operation at the correct frequency.



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