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operational amplifiers 2nd phần 7

RFID cung cấp trách nhiệm ở tất cả các điểm trong chuỗi cung ứng. Thiệt hại hàng tồn kho và ghi-off do co ngót có thể được giảm đáng kể bằng cách có một chuỗi cung ứng có trách nhiệm hơn. Khả năng để theo dõi các mục trong suốt một chuỗi cung ứng có thể giúp đỡ trong việc ngăn ngừa những tổn thất này, | 160 RESPONSE OF FEEDBACK AMPL. IERS When input voltage PỊn is a step function with magnitude Ko Equation 8.67b is applicable and K ui 0 becomes Fou t s 1 - 1.23e 3-7 1 0.23 k-. o.ds- 6.72 ns This is shown as graph c in Figure 8.8. It can be seen that it is slightly slower than the transient response with fL fz 50 MHz shown by graph a . Thus lowering fL from 50 MHz to 40 MHz is unfavorable to the transient response. When Cị is 5 pF then by use of Equation 7.45 c Ct 1. N dc _ I N.dc u Á ỉvÍÍl Also c. 5 pF ------------------ s 21 pF. 20 647 MHz 40 MHz - 1 1 1 R _ _ _ 1 QA Q 2nfLCr 2n 40 MHzX21 pF and from FN.dc R R Rf Rr . Rf 190H F i.dc These values are less than those of Example 8.16 Rf 637 Q and R 33.5 ÍĨ for graph a in Figure 8.8 they are also less than those of Example 8.21 Rf 1370 fl and R 72 fl for graph b in Figure 8.8. Thus the use of ft 40 MHz is unfavorable for operating speed as well as for Rf and R as compared to the use of fL f2 50 MHz of Examples 8.14 8.15 and 8.16 graph a in Figure 8.8 as well as compared to the use of fL 64.9 MHz of Example 8.21 graph b in Figure 8.8 . 8.33 Lag-Lead Compensation In this case in the frequency domain and Fr FN ic where dc 1 if fv 1 Ĩ 7Á fl Á fv fl- 8.74a 8.74b 8.74c A 1 j 1Xl 8.3 OAs WITH A Adl7 l iflfM iflM 161 Figure 8.15 illustrates the magnitude I as well as ll Fjvl and the resulting Afw . Note that Figure 8.15 shows equally spaced corner frequencies fl fL Ĩịj fc and f2 This is only for the purpose of the illustration in reality these are rarely spaced evenly. However the sequencing of the corner frequencies given by Equation 8.74c has to be followed. From Equations 8.74a and 8.74b feedback factor AFN can be written . p __AjcFm __J 4- if fu 1 j ÁXl j 2 1 j Á 8.74d FIGURE 8.15 Piecewise linear approximations of Bode plots for lag-lead compensation. Light lines illustrate A from Equation 8.74a and l Fjvl from Equation 8.74b. The piecewise linear approximation of the resulting IM vl