| 摘要 |
PURPOSE:To obtain an output video signal without the fluctuation of a frequency band regardless of a gain adjustment by consisting an amplifier utilizing the characteristics of a D/A converter. CONSTITUTION:So that, in a D/A converter, the fluctuation of a reference voltage is equivalent to that of an output voltage and the size of the fluctuation is decided by a digital input value of the D/A converter, the gain of an amplifier can be adjusted without changing the frequency band when the converter is utilized as the amplifier by adding an input signal to the input terminal of the reference voltage. Then, the sampled value of the black level of a video signal inputted to a terminal 7 by a sample and hold circuit 9 a voltage value divided by the resistor R1 and R2 of the video signal are added. Also, a signal for a gain adjustment is impressed at a digital signal input terminal 2 through a ROM 5. The signal for the gain adjustment is inputted, for example, as three bit signal by which the gain of the video signal inputted to the terminal 7 can be adjusted and a video output signal can be obtained from a terminal 4.
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