slide 1010. ]6 E- S3 F) w6 Z4 L1 \6 S+ [
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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. / A$ ~3 q) c( U
The signal bandwidth is determined by RF and not by the circuit gain.& t) h) P: C" g7 j
The circuit gain is independently set with RS.- z, X6 F) b4 _8 e1 f- F
The signal bandwidth remains stable for all gain settings . 4 y9 W- o) B9 z4 g; pEven for unity-gain operation, an RF resistor is required. $ u O. O* W" |- ?) D# Y0 q9 j( zThe 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. / o4 E. v3 v) C5 k8 E* ]; E
slide 1020 w% b0 v1 H: |& m8 M+ L2 J0 z) {% P. H. |6 [% B t( z
(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. # _% z/ P( ]5 m' A(2) For a given RF, frequency compensation can be optimized.2 r5 ~0 |# N" P" |8 M- e
(3)Suitable for high frequency applications.9 j" s! A$ ~: S; ^9 I* o3 O* |