| 摘要 |
PURPOSE:To prevent the leakage to the base due to capacitance between collector and base, by making different the phase of the reference subcarrier wave for B-Y signal demodulation by 180 deg., applied to the common base of each differential amplifier. CONSTITUTION:The reference subcarrier wave for B-Y signal demodulation having the phase difference of 180 deg. is outputted at terminals t13, t14 from a reference subcarrier wave oscillator 18 of a reference subcarrier wave generating section 35 and it is applied to each common base of transistors (TRs)Q13-Q16. Further, the reference subcarrier wave for R-Y signal demodulation having the phase difference of 180 deg. is outputted at terminals t15, t16 from a subcarrier wave phase inverting switch 20, and it is applied to each common base of TRs Q17-Q20. In this case, the output of the reference subcarrier wave oscillator 18 is applied to a subcarrier wave phase invertomg switch 20 in 90 deg. phase shift at the phase shift circuit 19. Thus, the subcarriers appeared at each switch of a differential amplifier constituting the demodulators are cancelled with each other and the leakage to the base due to capacitance between the collector and the base of the differential amplifier constituting the matrix circuit can be avoided. |
