Drive a capacitance load with a very large output resistance analog voltage source
I think more information could be added to your question to help get a direct answer, but here are a few thoughts.

Any analog signal could be driven really. There is simply different attenuation of the signal for different frequency components. If the analog signal is limited to be only composed of frequencies whose periods are much longer than the time constant of the circuit (output resistance * input capacitance) then no attenuation will occur and your signal will pass through easily. You could even work at higher frequencies if the analog signal is bandlimited since the attenuation would be approximately the same for all frequencies if the bandwidth is small. Then the comparator could easily do something such as flag overvoltages or undervoltages.

Hope this helps some.