Example: NIC U2=-R1i2 十 十 D R U1=U2(1) R4 (2) R RR i R U/i1-- input resistance The application of NIc R R 2 Telephone wires ,R=O NIC ∑2 2 R i  = − L (1) 1 =2 (2) 1 1 2 2 R i = R i 2 2 2 2 2 2 2 1 1 1 R R R i R i R i R i L L = − − = =   2 1 1 1 R R R i L = −  1 / i 1 − − input resistance Example: The application of NIC R − R NIC R = 0     Telephone wires 1 2 2 i 1 i − +  1 − +  2 RL NIC