slide 1010 * _& w3 D% U7 C$ A% X0 v$ P ( Y7 ?6 K X" ^2 PFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. - u5 q' j. U( k( m
The signal bandwidth is determined by RF and not by the circuit gain. : v1 c1 y' L" x& ^& T4 ?7 O* pThe circuit gain is independently set with RS. : k" l3 [4 D' ~; ? Q( H3 cThe signal bandwidth remains stable for all gain settings .; Y7 G$ c, m8 k6 g& g; ?% w
Even for unity-gain operation, an RF resistor is required. ) b0 F# j* y9 t; cThe 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. 8 w" S+ i4 s( ?0 p+ t4 c. m8 k
slide 1020 # w4 G6 {' Z4 |& b3 X . M$ c1 _7 F4 m# y$ w7 A(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged.2 \0 E q0 Q. m! R# i1 w$ E7 [
(2) For a given RF, frequency compensation can be optimized.- B$ s0 Q1 `8 l3 _5 }3 o% D
(3)Suitable for high frequency applications.0 @3 v0 e& r, x/ Q" p% V- R