| 摘要 |
PURPOSE:To improve the effective utilizing factor of an A/D converter by providing a gain variable amplifier to a pre-stage of the A/D converter and controlling it with a control signal from the post-stage. CONSTITUTION:The gain variable amplifier 12 is provided to the pre-stage of the A/D converter 13 and also a detection section 20 of an AGC control voltage consisting of a digital circuit is provided to the post-stage of the A/D converter 13 and the gain variable amplifier 12 is controlled based on an output LO of the detection section 20, allowing to apply the AGC to a television signal from an input terminal 11. Since a signal whose amplitude is made stable because of the AGC is A/D-converted, the bit number is utilized effectively as the A/D converter and the A/D converter having a comparatively low bit nubmer is used. |
