| 摘要 |
PURPOSE:To achieve the switching to an analog three-primary color signal with a simple circuit constitution, by making the switching of a voltage setting luminance level of background and character with a luminance designation signal and connecting a setting voltage to a switch circuit switched with a digital three-primary color signal. CONSTITUTION:Voltages VB1, VB2 of resistors R1, R2 of a variable resistor 12 are applied to the base of TRs Q4, Q3 as voltages VQB1, VQB2 via transistors TRs Q2, Q1 constituting a buffer circuit. Since the TRQ3, Q4 are constituted differentially, when a luminance designation signal YD is 1 and the background part is designated, a voltage VE is almost voltage VQB1 because of conduction of a TRQ5. When digital color signals RD, GD, BD are applied to input terminals 4-6 as 1, switches 14-16 are opened, and the voltage VE is applied to the base of TRs Q6, Q7, Q8. Thus, analog color signals RA, GA, BA are outputted to output terminals 8-9. Thus, the signal switching is constituted with a simple circuit and the adjustment between the luminance and the contrast is made without changing the rate of the luminance. |
