R-C circuit differentiator is classic with passive components that can   
   differentiate voltage signal. For step input R-C circuit differentiator makes   
   spikes on the output, so it differentiate step input signal better then the   
   op-amp differentiator circuit.   
    Now, there is a new tutorial    
      
      
   http://www.cirvirlab.com/index.php/electric/103-r-c-circuit-differentiator.html   
      
      
   and online simulation   
      
      
   http://www.cirvirlab.com/simulation/r-c_circuit_differentiator_online.php   
      
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