I'm having a bit of trouble designing a differentiator with an adjustable Td.
The main problem is with instablility, i have the basic idea for an op amp circuit.
The differentiator is going to be used within a PID controller so stablility is quite
important.
Put a resistor in series with the capacitor. This would change a little your overall frequency response, but you can make to be a diferentiator in the frequency range of your signals.