| 摘要 |
PURPOSE:To prevent waveform deformation from being generated to an input signal with a small amplitude by changing the direction of a charging current flowing to an integration device in response to the code of the most significant bit of a digital signal through the complementary constitution of the circuit. CONSTITUTION:Digital data of the most significant bit (MSB) and of bits other than the MSB are inputted respectively to terminals 22 and 23. Further, counters 9, 24 are changed over by current switches 6, 7 and 27, 28 in response to the value of the MSB. Moreover, a changeover circuit 34 adds 1 to the data without any change when the MSB 1 and after inverting the data other than the MSB and sets the data to the counters 9, 24. Then a capacitor 2 is charged from current sources 4, 5 and 25, 26 to obtain an analog value in response to the digital data. When the MSB is logical 1, the conductive period of the constant current source 5 of the low-order bit side is made longer as the data other than the MSB is increased at first and the constant current source 4 of the high-order bit side is also conducted next. On the other hand, when the MSB is 0, the constant current sources 26 and 25 of the low-order and the high- order bit side are operated similarly above as the data other than the MSB is decreased. |
