I am working on multi-channel DAS. I am using AD7982 in the signal line. The dynamic range of this ADC is 5V p-p differential with a reference of +5V. The receiving signal dynamic range is 20V p-p. In a application circuit given in the datasheet of AD8475, it is used to drive AD7982. But AD8475 with a gain of 0.4 the signal dynamic range is attenuated to 4V p-p. So, I am loosing a dynamic range of 1V. So, I am thinking of using external resistors to configure AD8475 to give a gain of 0.25. I can choose the values of resistors easily. But how to select the proper resistor which has similar drift coefficients of these internal resistors used.
Please suggest on this.