A video and sound IF processing IC with automatic tuning loops

A new video and sound IF processing IC (VIF/SIF IC) for use in TVs and VCRs has been developed. The IC makes possible automated VCO free-running frequency adjustment in the video IF section. The automated adjustment has been realized by virtue of a double-loop PLL equipped with a reference oscillator. Furthermore, a quadrature FM detector circuit built around a 90-degree phase shifter using a gyrator was employed in the sound demodulator circuit. The circuit eliminates the need for not only external components but also external adjustment. Thanks to these automated adjustment technologies, the VIF/SIF IC which almost totally obviates the need for external adjustment could be developed