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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. 3 N4 [1 j/ K. A( V, B3 h* ]
The signal bandwidth is determined by RF and not by the circuit gain.: N4 |$ O( S: @! v9 ^ { [4 S
The circuit gain is independently set with RS.
+ B8 |0 W2 E5 R$ m% V0 b1 W9 U( \( z+ DThe signal bandwidth remains stable for all gain settings .
. J, e0 q% T |' g1 g5 `( h- r, oEven for unity-gain operation, an RF resistor is required.2 g" M' V5 ?/ `+ C* a- q; L3 g
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.) h- C8 G5 h9 {- x$ D- J) H' m3 u% `
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