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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. - y# H: A1 F4 QThe signal bandwidth is determined by RF and not by the circuit gain. ; q6 d5 K) x6 `. z/ x% DThe circuit gain is independently set with RS.7 Q# [+ r" H. n& u$ K; U
The signal bandwidth remains stable for all gain settings . + Q' J$ Y9 X8 T% ZEven for unity-gain operation, an RF resistor is required. 2 R3 u; R% E* xThe 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. 9 t9 g8 t" _# ~
slide 1020 + M5 l) C: c J! s% B& e ; d% e( x' A; f( j: {2 v1 N) v(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 7 ?6 A. r( L k; @$ w(2) For a given RF, frequency compensation can be optimized.2 }6 _7 _) J* E8 g+ d
(3)Suitable for high frequency applications.6 F8 c0 h1 P+ n9 p4 {# x8 [" t; K: c# j