| 摘要 |
PURPOSE:To constitute a source follower circuit in which the relation of input/ output voltage is linear and the ratio of input/output amplitude is one by connecting output of a variable bias circuit to the gate of a load current source TFT of the source follower circuit. CONSTITUTION:A variable bias circuit is constituted of a thin film resistor 21 and a P-type TFT 22 that makes source follower operation. The variable bias circuit makes source follower operation, and voltage VO' appears at a nodal point 29 for input voltage VI. Consequently, the current that flows in an N-type TFT 23 that forms a load current source is determined depending on VO', and the larger the VO', the larger the current and the smaller the VO', the smaller the current. For instance, in the case where capacitive load such as a liquid crystal panel is driven, the voltage between the gate and the source of a TFT 24 is determined to nearly fixed voltage VGS=VGSO by movement of the variable bias circuit. Consequently, the input/output characteristic of the source follower circuit becomes linear.
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