| 摘要 |
PURPOSE:To vary and set a gain minutely by resistance and switches of a small number by connecting in parallel a series circuit of the resistance and the switch, to the switch connected to an input resistance or a feedback resistance of an operational amplifier. CONSTITUTION:Each resistance and each switch are connected in series, and one switch, for instance, as for a switch SW12 adjacent to an SW11, a series circuit of the SW12 and a resistance Rs 2 is connected in parallel to the SW11. Also, one end of the SW11, 12, etc. is connected to a signal input terminal A, and the other end of a resistance Rs 1 is connected to an inversion input terminal B of an amplifier. In the same way, with regard to a resistance Rf1, and SW21, etc., too, a combination of other switch and resistance is connected between an amplifier output terminal C and the inversion input terminal B. By forming in this way and controlling each switch, the gain is varied and set minutely by resistances and switches of a small number. |
