Vo(t) = RC (dVi(t)/dt). Suppose you have a triangle waveform as input to the differentiator with 100pF capacitance and 100 Ohms. The peak to peak voltage of the triangle waveform is 10Vpp and its frequency is 100k Hz.
What output would you expect? What would be the peak to peak voltage at the output?
What is the input impedance of the differentiator at f = 0 and f = +infinite? what is the impedance of the capacitor at these two frequency extremes?