Matsushita Electric Industrial Co., Ltd.

Yasuyuki Sato

Namio Yamaguchi

Apparatus for demodulating color difference signals from a chroma signal in a color television receiver set includes first and second differential amplifiers and a matrix circuit comprising a constant current circuit. Output terminals of the differential amplifiers and the matrix circuit are connected to a power supply through load resistors of the same resistance, respectively, through which D.C. currents of the same magnitude are passed. Resistors for combining signals are connected to the load resistors, and a common chroma signal is applied to the first and second differential amplifiers while sub-carriers of different phase are applied to the first and second differential amplifiers to effect synchronous detection to demodulate color difference signals of different demodulation axes across the load resistor. With this arrangement, a plurality of stable color difference signals of uniform D.C. level can be produced and the number of terminal pins required can be reduced so that the demodulation apparatus is readily implemented in an integrated circuit structure.

Color demodulation apparatus

A color signal processing apparatus, particularly a circuit for generating a color sub-carrier wave for demodulation, used in a color television receiver set to demodulate a carrier color signal to reproduce a color image, is disclosed. The apparatus comprises an oscillation circuit including four differential amplifiers to synthesize oscillation signals having phases which differ 90.degree. from each other to produce a color subcarrier wave, a color-phase adjusting circuit for changing phases of the oscillation signals from the oscillation circuit by changing bias voltages of the differential amplifiers, and a phase detection circuit for comparing the phases of the oscillation signals having the phases changed by the color phase adjusting circuit with a phase of a color burst signal to change the bias voltages of the differential amplifiers in the oscillation circuit depending on the comparison.

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Takatsuki, Japan

Yasuyuki Sato