ENI (Inv) ①b 22CM IGURE 27.3 A model for a practical op amp illustrating nonideal effects. Source: E J. Kennedy, Operational Amplifier Circuits, Theory and Applications, New York: Holt, Rinehart and Winston, 1988, Pp 53, 126. With permission. effects of the PSRR and CMRr are represented by the input series voltage sources of A upply /PSRR and M/CMRR, where AVsupply would be any total change of the two power supply voltages, Vde and vde, from their nominal values, while VM is the voltage common to both inputs of the op amp. The open-loop gain of the op amp is no longer infinite but is modeled by a network of the output impedance Zout(which may be merely a resistor but could also be a series R-L network) in series with a source A(s), which includes all the open-loop poles and zeroes of the op amp as (1+…) A(s) (27.5) 1+ where Aot is the finite dc open-loop gain, while poles are at frequencies Opl,(p2,... and zeroes are at Ozi etc. The differential input resistance is ZIN, which is typically a resistance RIN in parallel with a capacitor C Similarly, the common-mode input impedance Zom is established by placing an impedance 2Zcm in parallel e 2000 by CRC Press LLC© 2000 by CRC Press LLC effects of the PSRR and CMRR are represented by the input series voltage sources of DVsupply /PSRR and VC M /CMRR, where DVsupply would be any total change of the two power supply voltages, V+ dc and V– dc , from their nominal values, while VCM is the voltage common to both inputs of the op amp. The open-loop gain of the op amp is no longer infinite but is modeled by a network of the output impedance Zout (which may be merely a resistor but could also be a series R-L network) in series with a source A(s), which includes all the open-loop poles and zeroes of the op amp as (27.5) where AOL is the finite dc open-loop gain, while poles are at frequencies wp1, wp2 , . . . and zeroes are at wZ 1, etc. The differential input resistance is ZIN , which is typically a resistance RIN in parallel with a capacitor CIN. Similarly, the common-mode input impedance ZCM is established by placing an impedance 2ZCM in parallel FIGURE 27.3 A model for a practical op amp illustrating nonideal effects. (Source: E.J. Kennedy, Operational Amplifier Circuits, Theory and Applications, New York: Holt, Rinehart and Winston, 1988, pp. 53, 126. With permission.) A s A s s s OL Z p p ( ) ( ) ( ) = + Ê Ë Á ˆ ¯ ˜ + ××× + Ê Ë Á ˆ ¯ ˜ + Ê Ë Á ˆ ¯ ˜ + ××× 1 1 111 1 1 2 w w w