| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a gain variable amplifier whereby multi-stage gain adjustment can be performed with a small number of switches, a setting gain is not effected by the on-resistance of the switches, and a gain amount with high accuracy can be obtained. <P>SOLUTION: The gain variable amplifier is configured by connecting a noninverting input terminal of an operational amplifier 9 to a signal input terminal 1, connecting an output terminal of the operational amplifier 9 to a signal output terminal 10, and connecting a feedback circuit between the output terminal and an inverting input terminal of the operational amplifier 9. The feedback circuit comprises: attenuation sections 4 to 7 connected in series with the output terminal of the operational amplifier 9; a changeover section 8 comprising switches S3 to S7 and resistors R1 to R5; an attenuation section 3; switches S21 to S28 for selecting the attenuation amount of the attenuation section 3; an attenuation section 1; and switches S11 to S18 for selecting the attenuation amount of the attenuation section 1. The on-resistance is the same for the switches S3 to S7, and the resistors R1 to R5 have the same resistance. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
