| 摘要 |
PURPOSE:To remove an overcurrent due to ineffective AGC at the time of power feed at an AM radio receiver, by comparing the potential of a charging circuit, charged by a power voltage, with a reference potential and then by suppressing a detection signal by the comparison output. CONSTITUTION:Comparator H compares the charging potential of capacitor C1 charged by charging circuit I charged by a power voltage with reference potential V1; when potential V1 is greater, cutting-off circuit G is put into operation to cut off detection circuit F and when the charging potential of C1 is greater to the contrary, circuit G is stopped from operating. Therefore, although high-frequency amplifier B, frequency converter C, intermediate-frequency amplifier D, detection circuit F, etc., operate immediately with power switch S ON and the largest gain can be obtained, the charging potential of C1 is lower than potential V1 at this point in time, and consequently a detection output is cut off to prevent an overcurrent from flowing. When the operation of AGC circuit K becomes normal, the charging potential of C1 exceeds potential V1 and circuit H turns OFF circuit G, thereby outputting a received signal of an adequate level. With switch S OFF, charged C1 is discharged by the output of comparator J. |
