| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a multi-stage variable gain amplifier capable of having a wide variation range in a reception signal level. Ž<P>SOLUTION: An input signal is output as a differential signal in an active balun 111. A variable attenuation section 120 outputs a signal, where the input differential signal is attenuated by an attenuation factor selected from fixed attenuation factors. A variable gain amplification section 140 has amplifiers 141, 151 and a plurality of switches. The amplifiers 141, 151 amplify the input signal by a fixed gain, and outputs an output signal, where the input signal equals bias potential. The variable gain amplification section 140 operates in conjunction with the plurality of switches to selectively bypass the signal of the amplifiers 141, 151 for output. An output buffer amplifier 171 amplifies a signal input from the variable gain amplification section 140 for output. The multi-stage variable gain amplifier sets gain at the variable attenuation and variable gain amplification sections 120, 140, thus obtaining a necessary gain. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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