The simplest solution for the best DC accuracy is to use a low-offset (<10µV) auto-zero amplifier such as the LTC1150 or LTC2054. For a wider output swing, a second buffer amplifier such as the LT1010 can be incorporated in the loop. The LT1012 is a good intermediate output amplifier which achieves moderate speed (120µs settling) and good accuracy (±25µV offset) with low power (11.4mW). For applications where fast settling time is important, AN120 “1ppm Settling Time Measurement for a Monolithic 18-Bit DAC” offers another discussion of 18-bit DAC settling time and op amp selection. For high speed applications a good choice is the LTC1468, which settles a 10V step to within ±1 LSB at 18-bits in 2.1µs. Note that the ±75µV max offset will degrade the INL at the DAC output by up to ±0.9LSB. For high-speed applications demanding higher precision, the amplifier offset can be nulled with a digital potentiometer.