7 \ v' A, ?7 Y2 u( q" h9 N" `For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. / G5 |7 K( J# j# u7 P2 Y: j. b
The signal bandwidth is determined by RF and not by the circuit gain. % B* D; `6 J( ]" s% pThe circuit gain is independently set with RS.+ d0 s; `- X$ V1 Z
The signal bandwidth remains stable for all gain settings . 9 o4 A! l: h& Z' V8 TEven for unity-gain operation, an RF resistor is required. 7 t) ]& w6 Z- \' v/ nThe 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. 6 q6 e: S( z1 P) U5 Z! q9 [
slide 1020 8 W! v5 c" o) J3 f$ M0 {$ h3 S6 [# t
(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 5 ~9 g6 Q$ Q/ h# b, o(2) For a given RF, frequency compensation can be optimized. 9 x" P0 D3 ~) v% ]- `, b(3)Suitable for high frequency applications. * D/ i7 \% k1 A4 S: h8 E