| 摘要 |
PURPOSE:To set input impedance of an analog signal to 2R, make a device into an intergrated circuit, and enhance conversion speed and its accuracy by removing a resistor corresponding to the most significant bit of a R-2R type ladder resistance circuit network which is connected with constant current source. CONSTITUTION:The ladder D/A converter is composed of the constant current source 1 corresponding to the number of bits, n, of an output digital signal, R-2R type ladder resistance circuit network with n-stages and the current switches 2 which is installed between each output of the current source 1 and each connection point of the circuit network 3. Each switch of the switches 2 is individually opened, closed and controlled according to the bit logic level of input digital signal. The resistance value R is connected between respective contact points adjacent the circuit network 3, and between the ground point and contact point of the least significant bit. Coping with from 1-digit lower bit than the most significant digit bit to 1-digit upper bit than the least significant digit bit, the resistance value 2R is connected. Reduction in output impedance of an analog signal allows improvement of conversion speed and its accuracy. |
