in AN-691 the AD8314 is precluded from use in low frequencies because of a series capacitor at the input.
Is this true for all frequencies below 100Mhz or is there a way to operate it at 15-65 Mhz?
Yes, it is true at all frequencies below 100 MHz. If you need to operate at 15-65 MHz, there are a number of other options such as AD8310.
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