| 摘要 |
PURPOSE:To realize high accuracy not requiring adjustment such as trimming by generating a constant current to each current extracting line and forming a weight current with the change in the total connecting number of the current extracting lines. CONSTITUTION:Switch circuits SW1-SW8 apply switchingly output currents I1-I8 of constant current sources 11-18 to current extracting lines 21-28 in time division. As a result, an equal constant current I0 averaging the current error of the current sources 11-18 is obtained to the extracting lines 21-28. Then binary-coded weight currets 4I0, 2I0 and I0 applied to bit output lines L1- L3 of high-order 3 bits most important for high accuracy are formed by changing the number of summing of the extracting lines 21-27. The effect of the error of the current sources 11-18 is very less and the adjusting operation such as trimming is not required. Furthermore, a D/A converter comprising a resistance circuit is used for a low-order bit and since the effect of this part given on the accuracy is very less, the trimming of the resistors is not required. |
