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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. 7 t; q2 B+ @$ W4 Q. u/ b: V
The signal bandwidth is determined by RF and not by the circuit gain." m! N- }/ I' `! e' m
The circuit gain is independently set with RS.) q/ c% W9 V5 z, c5 Z c
The signal bandwidth remains stable for all gain settings .( Z# d: H3 C1 B7 @5 s4 m
Even for unity-gain operation, an RF resistor is required.) v- [, b9 Y O6 g0 N' B
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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