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slide 1010( q% e- z. b8 ^/ n( }2 _
7 h) V* M" A- F6 ]6 J7 g: p( XFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. , \5 }7 t; P$ ^% g+ l, x: z
The signal bandwidth is determined by RF and not by the circuit gain.
. I$ c3 h: E7 _; k8 _$ C% ^The circuit gain is independently set with RS.7 H3 \) d# o5 M4 ` r
The signal bandwidth remains stable for all gain settings .: t) E& Q# J7 g6 k9 d) b
Even for unity-gain operation, an RF resistor is required.- C: x# N. l T1 @4 G5 |
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.. x) j- b% U" \) [" g, s& x% d4 |* r
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