| 摘要 |
PURPOSE:To suppress a leakage signal of a switching signal incurring deterioration of picture quality by coupling the 2nd differential amplifier for signal switch to the 1st differential amplifier of a signal switching circuit, giving a signal current and a DC current to the former and giving a DC current brought into the non-signal state to the latter. CONSTITUTION:Trs Q1, Q2 constitute a switching differential amplifier to which a signal current source I1 and a DC current source I2 are connected, Trs Q3, Q4 constitute a switching differential amplifier to which a DC current source I3 is connected. Then figure (a) is a signal current waveform to be switched, a collector output waveform of the Trs Q1, Q4 when a switching signal shown in figure (b) to a terminal 12 is respectively shown in figures c, d and an output waveform of a switching signal reference DC voltage applying terminal 13 is shown in figure (e). That is, only a leakage signal of a switching signal generated by the signal switching circuit is generated by the signal switching circuit of the non-signal input, the signal obtained by the signal switching circuit and the leakage signal are inputted to differential amplifiers Trs 5, 6 of the next stage and only the leakage signal is eliminated by the function of common mode rejection. |
