JPS6411487A - Brightness control limiting circuit - Google Patents

Abstract

PURPOSE:To easily set a limiter by applying the limiter to a brightness control according to the same direct current bias as the direct current level of a color difference signal output at the time of a silent signal set by the bias circuit of a demodulating circuit. CONSTITUTION:The color difference signal output is inputted to the base of a transistor TrQ5 through a color difference signal output terminal 7 from the demodulating circuit 12, a luminance signal from a luminance signal processing circuit 2 is pedestal clamped and inputted to the base of a TrQ4. The base of a TrQ4 in which the direct current bias the same as the direct current level of the color difference signal output at the time of the silent signal applies the limiter to the brightness control through a bias terminal 8 is connected from the circuit 12. The pedestal level (base potential of TrQ4) of the luminance signal is changed according to the brightness control. However, since the direct current level of the color difference signal output terminal 7 an the bias terminal 8 is equal, the base potential of the TrQ4 is not raised above the base potential of the TrQ5. Accordingly, the pedestal level of the primary color signal of an output terminal 11 has the limiter applied substantially at OV and is not lowered therebelow.