A Hybrid Thick-Film Chroma Demodulator and Color-Difference Amplifier

An experimental hybrid thick-film module has been developed that performs the functions of color demodulation and amplification in a color television receiver. The module consists of three principal circuit sections, all included on one 1 x 2 inch substrate: 1) two dual-diode color demodulators, 2) color-difference amplifiers, and 3) a four-diode dc restoration circuit that clamps all three color-difference signals. The circuit normally consumes about 9 watts from a +250-volt dc supply. Circuit features and design parameters are discussed, and the construction of the module is described. The module contains 49 components which include ceramic cup packaged transistors and diodes, screened resistors and capacitors, and high-voltage chip capacitors. Thermal limitations imposed by various packaging concepts are reviewed, and several novel types of heat sinking and encapsulation approaches are described. Results are presented on electrical, thermal, environmental, and functional tests of this color TV circuit module.