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slide 10105 I$ f6 s8 X# n# Q9 l! Q' V) c
% e6 B. T! H2 [; [9 IFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. ; k& I8 d2 c+ ^4 h6 U
The signal bandwidth is determined by RF and not by the circuit gain.! H, e) f# T! l
The circuit gain is independently set with RS.: G L" B5 q( c) K0 @$ N: V
The signal bandwidth remains stable for all gain settings .& [5 T) U+ N$ X$ Z5 Z
Even for unity-gain operation, an RF resistor is required.
; ]6 ^; U- P; }0 S0 H ~" |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.* D9 U: ?7 S6 C6 c( m
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