| 摘要 |
PROBLEM TO BE SOLVED: To provide an ASK receiver which can determine data extending from an infinitesimal input level to a large input level. SOLUTION: A variable gain amplifier 2 amplifies an amplitude change component of an ASK signal of an input terminal 1 to a signal level which can be stably determined, and a rectifier circuit 4 removes a carrier component of the ASK signal from the output and takes out a low frequency component of the ASK signal to be outputted from an output terminal 6 after a waveform shaping by a component 5. A gain control is performed to the output of a detecting wave circuit 3 according to an output amplitude of the variable gain amplifier 2. The constant current I of a constant current circuit 10 is applied to the output of the detecting wave circuit 3, the gain is controlled so that a total of a detecting wave current of the variable gain amplifier 2 output and the constant current I, and a voltage by a product of a load resistance R are equal to a reference voltage Verf. In case of the maximum gain upon no input and infinitesimal signal, as for the detecting wave circuit 3 output, only a detecting wave current of the variable gain amplifier 2 output restricted appears for the constant current I, the maximum gain of the variable gain amplifier 2 is restricted, the gain is increased compared with the case where no constant current I exists, and an excellent receiving sensitive characteristic is obtained without generating an output noise. COPYRIGHT: (C)2005,JPO&NCIPI
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