D. C.and A. C. characteristics of non-ideal operational amplifiers are examined from a general viewpoint

and a set of useful expressions and conclusive results are obtained. The suggested linear approximation model takes into considerations the effects of CMR in a more reasonable manner in comparison with the commonly-used models. The constraints on the linear approximation of OP’s in A.C.case are discussed. Besides the slew rate limitdE/dt|max or the full power bandwidth ωp

there may be otherrestrictions such as d2E/dt3

etc. In some cases

the frequency response of CMR may influences thetransfer characteristics of closed loop OP’s. The useful range over which the previous expressions are valid were given. Finally

the suppression of supply noise

the measurements of high frequency gain and other problems are analysed.