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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.
2 h/ d. f1 o: \0 h, C/ o# wThe signal bandwidth is determined by RF and not by the circuit gain.
: `8 ~' `8 A! }3 L$ |/ }The circuit gain is independently set with RS.
% p0 j% I: Y7 t2 R% iThe signal bandwidth remains stable for all gain settings .) s9 z2 a: L0 S# I: X
Even for unity-gain operation, an RF resistor is required.6 t. I$ `" @# ?1 q& Z
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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