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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. ( A; n" u: t' ~' \4 n2 T9 I
The signal bandwidth is determined by RF and not by the circuit gain.; W/ x7 @6 c" `# A
The circuit gain is independently set with RS.- G5 Z! Q% n6 ^
The signal bandwidth remains stable for all gain settings .5 T m; {7 ~/ t" r3 w
Even for unity-gain operation, an RF resistor is required.3 R; v1 U' I1 E' A0 M' C, j
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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