Subtractor Circuit

Hello my question is i want to declare on the Pspice subtractor.But i have no ideas how to design the circuit.Does anyone know about subtractor.I found many pages in internet but i dont see real circuit design.Our teacher said to me this device has resistor capacitor and one more element.İf you have picture about circuit design can you share with me?

maybe you mean an op amp or diff amp used in subtract mode (differential inputs). or maybe you mean a differentiator, which outputs the differential vs time of an input (the output is proportional to the rate and direction of change of a voltage).

shown below is a differentiator with input and output (forgive the crude representation) voltages. the decay slope of the output voltage is determined by the time constant 0.67(RC).