slide 1010 G5 O/ q( `8 S; ~5 Q! Z ! m9 h' h, V( xFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. + T; y# p' D" c0 s1 W" i1 d
The signal bandwidth is determined by RF and not by the circuit gain.$ `2 E/ f( u9 M0 Z; P8 O
The circuit gain is independently set with RS. # X) f$ ~& \6 |The signal bandwidth remains stable for all gain settings . A0 W6 t2 A/ q8 S* [4 r' |Even for unity-gain operation, an RF resistor is required.: K+ o' H5 f! ~
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. 9 L% D' U% B1 z0 ?8 a
slide 1020 4 q$ c2 T- u( {7 K4 {. e, r/ x4 t4 n) U) ~; H
(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. & O4 t7 B" N, ](2) For a given RF, frequency compensation can be optimized. 4 J5 e3 ]3 N/ \/ e% x9 c% J" d/ N(3)Suitable for high frequency applications. 8 g3 O# {3 u: }5 Q! w4 e