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' k; E; c2 I- H, [. B1 Q, o, D5 l! _For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. " b+ a+ a; q5 q# O) b! q
The signal bandwidth is determined by RF and not by the circuit gain.
# Z! X, {; |4 o7 o! pThe circuit gain is independently set with RS.
# t* K- N4 ~3 bThe signal bandwidth remains stable for all gain settings .; X) t/ f5 D9 a L( A6 R$ A3 u0 x/ W* [( m
Even for unity-gain operation, an RF resistor is required.
" r S+ Q/ ]$ C% G' G& u2 gThe 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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