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slide 1010/ ` R7 R2 j% Y) I2 {
+ W# t: p; a6 P2 u, U$ _* Y. \For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF.
. Z f6 n# x' h' @4 c: O2 _, PThe signal bandwidth is determined by RF and not by the circuit gain.- O$ O1 C. Y1 N6 E
The circuit gain is independently set with RS.. O. E9 C* ^" @6 Y, Z7 f
The signal bandwidth remains stable for all gain settings .6 N4 u t; R. g2 B- W+ |& z
Even for unity-gain operation, an RF resistor is required.! @* Y6 P: }0 d. 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.
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