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For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. % W% u! N% e- e/ l
The signal bandwidth is determined by RF and not by the circuit gain.' C Q1 a* @1 Q$ k
The circuit gain is independently set with RS. & T) a* v6 f5 C6 E0 F' y0 B8 nThe signal bandwidth remains stable for all gain settings . 6 W3 ^8 X- k5 EEven for unity-gain operation, an RF resistor is required.- L) s3 j$ c; c/ I( j
The best practice when designing with CFB op-amps is to use the RF values given in the datasheet and to adjust the desired gain level through RS.$ N+ w( J+ b1 u3 _/ V' G
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 7 r" N( M4 j0 g4 O7 u0 m& A L# R9 a(2) For a given RF, frequency compensation can be optimized.& ?' e9 ~. Y: |7 X) _6 E$ w6 s
(3)Suitable for high frequency applications.# r+ A. r _( Z7 I8 _% }