| 摘要 |
PURPOSE:To obtain an AGC function which does not respond to a modulated wave component of a signal but quickly responds to a variation of its level, by providing a switching device for switching the frequency characteristics of an LPF in accordance with a tuning state. CONSTITUTION:In an AM radio receiver having an automatic channel selecting function, a high band intercepting frequency of an LPF 14 is made high so as to quickly respond to a variation of a signal level in a wide band AGC detecting point, in the course of its automatic channel selection. On the other hand, after the tuning frequency has been decided, the high band intercepting frequency is made low enough so as not to respond to a modulated wave component of a signal. In this way, the AGC function is elevated by providing a switching device 15 for switching the frequency characteristics of the LPF 14 in accordance with the tuning state. |
