Modified Colpitts oscillator for driving an antenna coil and generating a clock signal

摘要

A Colpitts-type oscillator circuit suitable for use with electronic identification systems is disclosed. The oscillator circuit utilizes a pair of transistors coupled together with a feedback loop that includes a parallel LC circuit such that the output amplitude can be as high as a factor of 20 times the supply voltage or more while maintaining a high Q, low distortion output. The oscillator circuit is a modified Colpitts oscillator that includes a NPN transistor and a PNP transistor coupled together and a Colpitts type feedback loop containing a parallel LC circuit. The capacitance of the parallel LC circuit consists of at least two capacitors in series forming a capacitive divider which provides a low impedance feedback via the base of the NPN transistor into the emitter of the PNP transistor. The collector of the PNP transistor taps into the inductor of the parallel LC circuit such that the inductor is driven to resonance.