| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that the load of a microcomputer becomes heavy when the microcomputer performs software control to control the gain of an audio signal amplifier. SOLUTION: This attenuator 100 attenuates an input signal Vin and outputs the input signal Vin to an amplifier 30 for amplifying a signal to be applied to two input terminals. In a resistance group 10, a plurality of resistances R1 to Rn are serially connected, the input signal Vin is applied to one end and the other end is grounded. A switch group 12 includes a plurality of switches and connects a first output terminal 106 and a second output terminal 108 to connection nodes N1 to Nn. A comparison determining circuit 18 compares a data variable Dy corresponding to the current attenuation factor with target data Dx corresponding to an attenuation factor to be a target value and outputs an up signal or a down signal. A decoder circuit 14 selects a switch corresponding to digital data Dy outputted from an up/down counter 16 between first and second switch groups SWa and SWb by one at a time and turns on the selected switch. COPYRIGHT: (C)2007,JPO&INPIT
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