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For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. + X" h0 C) J7 e2 g; d' k+ `1 y
The signal bandwidth is determined by RF and not by the circuit gain. 8 R" Z3 V" E, V' U+ X3 P' [The circuit gain is independently set with RS.! s; i- G& \- P5 C
The signal bandwidth remains stable for all gain settings . S9 R& ]; f. UEven for unity-gain operation, an RF resistor is required.' p5 Z1 ~' s& T! p
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.( R2 u R8 { @& b& f; {' z
slide 1020 8 m" g6 }2 f, r' _+ ?4 `$ X/ \% \. | 2 L, w0 |. x1 j8 X4 z, Q) V(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged.- Y3 V( g- r! r- V6 E
(2) For a given RF, frequency compensation can be optimized.) ?" V" ^1 Y. l6 S0 y
(3)Suitable for high frequency applications.) O t) j( }# G' C# y