摘要 |
<p>A comb filter easily implementable as a monolithic LSI without using a large-capacitance capacitor is provided. A comb-like frequency characteristic is realized by two delay circuits for delaying a signal for mutually different amounts of time and an operation circuit for deriving a sum or difference of the outputs thereof. An input select switch selectively outputs, instead of an image signal, a test signal, which is a DC signal having a predetermined amplitude, during a blanking interval of the image signal. A detector controls the gain of a variable-gain amplifier, provided for the output of either one of the delay circuits, in accordance with a difference between the output signal of the comb filter in response to the test signal and a predetermined reference signal. That is to say, the gain of the comb filter is controlled by using a stable test signal as a control signal, instead of a burst signal contained in an unstable image signal. Accordingly, a large-capacitance capacitor, which has been required for stabilizing the control signal, is no longer necessary. <IMAGE></p> |
申请人 |
MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. |
发明人 |
DOSHO, SHIRO;YANAGISAWA, NAOSHI;OZASA, MASAYUKI;KURIMOTO, HIDEHIKO;OKAMOTO, TASUO |