| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that an output characteristic of a signal strength detection circuit is varied by fluctuation of power supply voltage. SOLUTION: The signal strength detection circuit is driven by the power supply voltage Vdd, and comprises: saturation differential amplification circuits 60-1 to 60-n which sequentially amplify input voltage Vin, and are continuously connected at a plurality of steps; full-wave rectifiers 80-1 to 80-n which rectify signals amplified by the saturation differential amplification circuits 60-1 to 60-n at each step, respectively; a current mirror circuit 100 for finding a signal strength detection current IO of an a sum of output currents of the full-wave rectifiers 80-1 to 80-n at each step; and a power supply voltage fluctuation suppressing circuit 110 which depends on the power supply voltage Vdd to change the amount of the current. Further, the output current of the circuit 110 is added to the signal strength detection current IO, and thus, power supply voltage dependency is reduced in the signal strength detection voltage Vrssi. COPYRIGHT: (C)2008,JPO&INPIT
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