In-phase proportional operation is series negative feedback. The output voltage is stabilized by in-phase comparison and inverse comparison, so voltage negative feedback is adopted. The inverse proportion is input from the inverting terminal, which introduces negative feedback, so the inverse proportion belongs to voltage parallel negative feedback, the feedback coefficient is 1/Rf, and the voltage amplification factor is RF/R. The noninverting input terminal is input from the noninverting terminal, which also introduces negative feedback, so it is voltage series negative feedback, the feedback coefficient is R/(Rf+R), and the voltage amplification factor is1+RF/R.