1、Operational Amplifier and its Intuitive Analysis ab oAca reverse phase input terminal (inverting phase input terminal) b in-phase input terminal (non-inverting phase input terminal) c common terminal (grounding terminal) o output terminal A open-loop voltage gain o Au u u(1) circuit symbol of op amp
2、 (2) two typical connection modes of op amp Au ouab A ouab o Au u uAu o Au u u+Authe mode of inverting input the mode of noninverting input (3) low-frequency circuit model of op amp uu ou A uuiR oRab uu ou A uuabinput resistance output resistance idealizing open-loop voltage gain iRoRA6 1 31 0 1 0 1
3、 0 1 0 05710 10iR o 0R A o Au u u=0uuthe currents through its two input terminals are equal to zero the voltage across the two input terminals is equal to zero uu ouiiinput port behaves as a short circuit input port behaves as an open circuit 00uuii(4) circuit symbol of ideal op amp Practice problem: As shown in the figure, calculate the ratio of output voltage uo to input voltage us. su1i 1RfRaibi2iouabSolution: ab 0uus a s111u u uiRRa o o2ffu u uiRR 12iiso1fuuRRo fs1u RuR
