A new FMX stereo decoder IC design

A frequency modulation extended (FMX) stereo decoder IC containing autotuning 19-kHz/38-kHz notch low-pass filters is discussed. The filters are implemented using OTAs (operational transconductance amplifiers) plus poly-poly capacitors. The autotuning techniques are used to overcome the effect of fabrication process parameter variations. A phase-locked VCO (voltage controlled oscillator) signal is used as master reference. The VCO was designed using a ceramic resonator and symmetrical reactance circuit, phase locked with the received pilot signal by the PLL scheme and adjustment free. The VCO is also used for demodulation of the subcarrier. The IC is fabricated using 2- mu m bipolar techniques and is assembled in shrink 32-pin plastic DIP.<
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