A new interface amplifier concept for fast D/A converters

A new interface amplifier is proposed which can tolerate an appreciable capacitive loading without affecting the settling time. It utilizes a low loop-gain approach with high internal bandwidth and excellent open-loop gain linearity. Most importantly, the amplifier is compensated at the input node rather than somewhat internally. As a result, the amplifier overdrive also can 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 500 pF and a load capacitance of 12 pF, the measured settling time is less than 70 ns to within /spl plusmn/0.05 percent for output-signal changes of /spl plusmn/10 V.