calculating input impedance with wye voltage divider in non-inverting op amp - Audio forum - Audio - TI E2E support forums
Op-Amp Inverting Amplifier | Ultimate Electronics Book
operational amplifier - Calculation of the input resistance of an op amp circuit - Electrical Engineering Stack Exchange
operational amplifier - Input Impedance of the Inverting Op Amp - Electrical Engineering Stack Exchange
Review of Linear Op-Amp Circuits We will quickly review the analysis & design of linear op-amp circuits that use negative feedback: Non-inverting amplifier. - ppt download