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# B1 ?; ] A( [" h, e# x; xFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. " d0 W, m# i& A. A$ B8 {
The signal bandwidth is determined by RF and not by the circuit gain.1 {7 u& |" r$ s* e( u& u9 p' g6 a7 B
The circuit gain is independently set with RS.) o& m/ }1 L$ i c9 I, K
The signal bandwidth remains stable for all gain settings .% e& K. r& |6 s9 X
Even for unity-gain operation, an RF resistor is required.
9 h, s7 c- b7 A3 A: I( G' R/ ?: 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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