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$ S* B n" Y! R* O2 ]+ T& [For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF.
( S; ]7 P5 F( }The signal bandwidth is determined by RF and not by the circuit gain.
2 G! [8 x6 V* O' K6 W) i0 PThe circuit gain is independently set with RS.
8 I1 o( B* c" LThe signal bandwidth remains stable for all gain settings ./ S7 g+ u4 j/ {
Even for unity-gain operation, an RF resistor is required.
$ L* b8 q/ x4 q! N/ FThe 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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