slide 1010 , D) f# D+ K1 ^1 {' F) Q9 a5 F" Y+ 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. ) S$ l# @. T, LThe signal bandwidth is determined by RF and not by the circuit gain.4 k P# ?- t8 H
The circuit gain is independently set with RS.3 B, K* ]; U; I5 K/ `& i
The signal bandwidth remains stable for all gain settings .* {/ x- O% r$ L& q h$ [7 p
Even for unity-gain operation, an RF resistor is required.# |$ U) p1 v$ X9 Z# A
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. ; M1 |: J8 a! i! M
slide 1020 1 k; \" R# j9 r4 V, K, Q + X' [$ X- Y, `% ^4 L O4 m W(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 6 |5 b( U2 h0 Z% [, L+ d- p(2) For a given RF, frequency compensation can be optimized.6 X, [* I; L: ^# b
(3)Suitable for high frequency applications.9 a' k8 D) O" `5 g0 t1 B$ e$ Q8 ?7 f