| 摘要 |
PURPOSE:To individually set at the time of the stationary and at the time of the transition of a PLL radio receiver and to share in plural bands by providing a switching circuit consisting of a resistance serially connected transistor. CONSTITUTION:The switching circuit formed by serially connecting the resistance R3 and a field effect transistor (FET)Q2 in parallel with an input resistance R1 is added. Accordingly, when a pulse is impressed at the time of charging a power source or at the time of the transition such as the switching of a frequency to the gate of the FETQ2 from the muting pulse generating terminal or the like of an LSI through bias resistances R4, R5, the FETQ2 is turned on, an input resistance value goes the parallel synthesized resistance value R of the R1 and the R3 and under the steady state, the FETQ2 is turned off and the input resistance goes to only the R1. In such a way, the input resistance value of an active low pass filter is switched, thereby, the radio receiver can be individually set at the time of the stationary and at the time of the transition.
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