Digital 12 Bit DAC Circuit with Variable Step Size
12-Bit Digital-to-Analog Converter (DAC) with variable step size . The step size of the converter is variable by selection of the high order data bits. The first DAC, A, has a stable reference current supplied via the 10.24 V reference IC and Rl. R2 provides bias cancellation. As shown, only the first 4 MSB inputs are used, giving a step size of 225/256 2.048/16 = 0.127 mA. This current supplies the reference for DAC whose step size is then 0.1275/256 = 0.498 µ. Complementary voltage outputs are available for unipolar output and using R3 - R4 = 10, Vout is ± 10.2 V approximately, with a step size (1 LSB) of approximately 5 mV. If desired an op amp can be added to the output to provide a low impedance output with bipolar output symmetrical about ground, if R5 = R6 within 0.05%. Digital 12-Bit dac Circuit Diagram Note That offset null is required, and all resistors except R2 and R3 should be 1% high stability types. By using lower order address lines than illustrat...