= Inverting RC high-pass amplifier
{title2=$H(\omega)=-i\omega R_fC/(1+i\omega R_iC)$}
An ideal <operational amplifier> with a series input <resistor> and <capacitor>, resistive feedback and a grounded noninverting terminal realizes the displayed <high-pass filter>. <Virtual ground> and <Kirchhoff's current law> give $H=-R_f/[R_i+1/(i\omega C)]$. Its <phase> is $-\pi/2-\tan^{-1}(\omega R_iC)$ in the $e^{i\omega t}$ convention. Equal resistances do not make its <phase> <frequency> independent.
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