| 摘要 |
PURPOSE:To prevent an abnormal operation in the event of an excessive input signal, by limiting a driving current applied to a variable impedance element in an ALC circuit. CONSTITUTION:A signal inputted to a terminal 1 is inputted to an amplifier A through a variable impedance element E. The amplifier A amplifies the input signal by specified gain, and outputs it from a terminal 5. In case the input signal is large, the variable impedance element E is controlled in accordance with magnitude of voltage of a portion which exceeds reference voltage, so that the input signal becomes small. Voltage for controlling the variable impedance element E is limited before the variable impedance element E is saturated. In this way, it is prevented that the output signal is distorted, by preventing that the variable impedance element E is driven excessively. |
