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2.7 Nonideal (i.e., real) operational amplifiers respond to both the differential and common-mode components of their input signals (refer to Fig. 2.4 for signal representation). Thus the output voltage of the op amp can be expressed as v O = AdvId +AcmvIcm where A d is the differential gain (referred to simply as A in the text) and Acm is the common-mode gain (assumed to be zero in the text). The op amp’s effectiveness in rejecting common-mode signals is measured by its CMRR, defined as CMRR = 20 log A d A cm Consider an op amp whose internal structure is of the type shown in Fig. E2.3 except for a mismatch Gm between the transconductances of the two channels; that is, G m1 = Gm − 21Gm G m2 = Gm + 21Gm Find expressions for Ad, Acm, and CMRR. What is the maximum permitted percentage mismatch between the two G m values if a minimum CMRR of 60 dB is required?