| 摘要 |
PURPOSE:To attain quick response even to a signal having much noise, by detecting whether the input level exceeds the dynamic range or not in the operating processing section in the AGC circuit and providing an AND circuit, an exclusive OR circuit and a delay element. CONSTITUTION:The gain of a variable amplifier 1 is set to the state close to the maximum gain when a signal (i) is ''0''. Since a signal having a large level is inputted after the signal (i) goes to ''1'', a level exceeding the dynamic range is inputted to the input of an operation processing section 5, the output of a comparator 5-3 goes to ''1'' and a signal (j) goes from ''0'' to ''1''. The output (k) of the exclusive OR circuit 11 goes to ''1'', an FF9 is reset and the output (i) goes to ''0'' gain. As a result, an output (d) of a comparator 3 is inputted to an up-input of an up-down counter 7, the counter 7 is counted up in the period of a clock input signal (a), resulting that the gain of the variable amplifier 1 is decreased to the normal state quickly. |
