A new interface amplifier concept for fast digital-to-analog converters

A new interface amplifier is proposed which can tolerate an appreciable capacitive loading without affecting time. It utilizes a low loop-gain approach with large internal bandwidth and excellent open-loop gain linearity. As a result, the amplifier overdrive can also be eliminated, provided that the rise and fall times of the converter's output current stay within prescribed limits. Contrary to the present high-speed D/A converter realizations, in this application only a low-current, low-power D/A converter is required. With an input capacitance of 350 pF and a load capacitance of 12 pF, the measured settling time of the new interface amplifier is less than 100 ns to within + or - 0.05% for output-signal swings of + or - 10 V.