This circuit shows the LT6203 driving an LTC1864 unipolar 16-bit, 250ksps A/D converter. The bottom half of the LT6203 is in a gain of 1 and buffers the 0V negative fullscale signal VLOW into the negative input of the LTC1864. The upper half of the LT6203 is in a gain of 10, referenced to the buffered voltage VLOW and drives the positive input of the LTC1864. The input range of the LTC1864 is 0V to 5V so for best results the input range of VIN is from VLOW, about 0.4V to about 0.82V. Figure 4 shows an FFT obtained with a 10.1318kHz (coherent) input waveform, with no windowing or averaging. Spurious free dynamic range is seen to be 100dB.