| 摘要 |
PURPOSE:To provide a variable gain amplifier in which a gain can be set from a circuit outside, the setting error of the gain can be reduced, a frequency characteristic can be satisfactory, and a noise can be reduced. CONSTITUTION:The input resistance of an arithmetic amplifier 1 is constituted of a circuit in which plural transistor switches 5-1-5-5 respectively having prescribed conductive resistances are connected in parallel. Then, the transistor switches 5-2-5-5 are selectively turned on by control signals added from control terminals 7-1-7-4, and the gain is controlled by the number of the transistor switches which are turned on. |
