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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. 9 v8 A& T, R8 r
The signal bandwidth is determined by RF and not by the circuit gain.
1 Q/ `/ k6 R# {9 o* V6 S* YThe circuit gain is independently set with RS.
- L/ G' z- J2 t$ o& ?0 x' gThe signal bandwidth remains stable for all gain settings .& [5 h6 p/ s# J. j: e6 ~& U
Even for unity-gain operation, an RF resistor is required.9 i7 X! o0 h% x6 O- o
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.
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