| 摘要 |
A video tone control circuit is implemented in an integrated circuit and comprises a sharpness control for differentiating a rise and fall of a video signal for controlling the amplitude of a high frequency component in the thus obtained video signal with a variable gain amplifying circuit for providing a video signal with the differentiated output superimposed thereon, and a softness control for changing an attenuation amount of a high frequency component in the video signal with a low pass filter. Either of the variable gain amplifying circuit and the low pass filter is enabled responsive to the level between a first range or a second range of the direct current bias voltage, while the other is disabled. When the direct current bias voltage is set in the first level range, the gain of the variable gain amplifying circuit is controlled so that the degree of emphasizing a high frequency component is changed, whereas when the direct current bias voltage is set in the second level range the degree of attenuating a high frequency component by the low pass filter is changed. A current mirror circuit for preventing fluctuation of the direct current voltage level is connected to the variable gain amplifying circuit. |
