is DC blocking necessary for an ADC board input?

[vahidkh6222]

I'm trying to drive the differental input of ADS5474 with an opamp single-ended to differential converter. I used the recomended opamp configuration and i took into account the source impedance and proper terminations.

but when i plug the source(a 50 ohm signal generator) to ADC board, the DC balance between + and - input pins of ADC looses. and i see 1volts DC offset between them. if the answer is yes then how?I used a 220 micro capacitance in series and I got the desired DC balancing but the gain of the driver became frequency dependent and noisy.

I should do the ADC sampling by about 180 MSpS!
thanks in advance

 

[FvM]

An ADC circuit can be designed for DC input. But how did you define input voltage range? Do you intended bipolar or unipolar range related to circuit ground? The latter must introduce an offset in input amplifier.