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' g; G. P/ _: B% P* _For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. 8 Z! R2 Q/ s2 G7 K
The signal bandwidth is determined by RF and not by the circuit gain.
( P" n/ r( t# t9 l0 }The circuit gain is independently set with RS. f+ r5 k/ x! k* ]9 Z
The signal bandwidth remains stable for all gain settings .3 T% c! c9 \8 J) x( d1 p; j5 T0 X! q* A
Even for unity-gain operation, an RF resistor is required., ~- z7 |& d5 A9 T& w
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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