Op amp differentiator ($V_{\mathrm{out}}=-RCd{V}_{\mathrm{in}}/dt$)

For an ideal operational amplifier with grounded non-inverting input, connect an input capacitor $C$ to the inverting input and a feedback resistor $R$ from output to that input. The virtual ground and Kirchhoff's current law give $C{\dot{V}}_{\mathrm{in}}=-V_{\mathrm{out}}/R$. The ideal response amplifies high-frequency noise, so practical differentiators restrict its operating band and maintain feedback stability.