| 摘要 |
<p>1294405 Colour television; transistor amplifiers RCA CORPORATION 13 March 1970 [21 March 1969] 12099/70 Headings H3T and H4F To process the luminance and chrominance signal component of a composite (NTSC-type) video signal separately, i.e. vary their relative amplitudes, the composite signal is fed to the base of transistor 13, Fig. 1, whose emitter is connected to a tuned circuit 18 adjusted to resonance at the colour subcarrier frequency (3.58 MHz). The frequency response of tuned circuit 18 is selected such that its impedance for the luminance signal components is less than the impedance of load resistor 16. Therefore the luminance signal components appear across load resistor 16 while the chrominance signal components alone are supplied to the base of transistor 21. As shown, the amplitude of the chrominance signal components may be varied by potentiometer 24. Load resistor 16 is common to the collectors of both transistors 13 and 21 so that the signals therefrom appear across resistor 16 combined i.e. at output 25, with no differential phase distortion. In a second embodiment (Fig. 3, not shown) the phase of the chrominance signal is inverted in the recombined composite signal, a third transistor being employed. Both components may pass through gain-controlled stages.</p> |
