5 t1 |0 I. U3 D$ p2 VFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. 1 K0 W3 g# ?0 GThe signal bandwidth is determined by RF and not by the circuit gain.: J) `8 T: L: S% ?$ }
The circuit gain is independently set with RS.% h* Y# O; c; |! D1 T1 `
The signal bandwidth remains stable for all gain settings . 3 u$ X$ u/ {4 B0 b* T* c3 ~- g" _Even for unity-gain operation, an RF resistor is required. , @: {; J- |: r" T0 g0 QThe 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 O! j/ G. L* _1 l# k, s
slide 1020 ; i; z9 J7 f9 y" }' ~& Z ' N2 p8 M8 S/ ^# ]& }5 M% @(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged.- N1 I1 X, g; x5 L6 I6 c# Y6 ]
(2) For a given RF, frequency compensation can be optimized. % Y8 R/ T9 _. b! r9 \(3)Suitable for high frequency applications.; t- T0 f4 r1 j6 L: Z1 M