An Integrated Frequency-Selective AM/FM Demodulator

The lack of integrated inductors is a significant drawback in the design of frequency-selective integrated circuits for broadcast and TV receivers. In many cases, a partial integration of the receiver sub-systems is possible by combining all the active elements in a monolithic package and leaving the tuning coils and the inductors external to the circuit. However, this compromise solution often represents only a marginal advantage over the conventional design. For integrated receiver circuits, phase-lock techniques present an alternate design approach which eliminates the need for inductors1. In such an approach, one uses a phase-locked loop ( PLL) system to perfonn the selectivity and the demodulation functions in a receiver. A detailed analysis of the PLL system as a tracking filter and FM demodulator has been extensively covered in the literaturel-3 and will not be repeated here.