slide 1010 $ ~6 Y* o0 n: f* n4 M9 E6 q ) r }. k+ y$ d( f+ UFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. . T& `$ A* i/ F) a2 aThe signal bandwidth is determined by RF and not by the circuit gain.) s Q' X0 p* c- L( y0 Z# F
The circuit gain is independently set with RS. z; y' g- y* o4 O) F- yThe signal bandwidth remains stable for all gain settings .% T. P/ C2 t; ?9 F$ Q
Even for unity-gain operation, an RF resistor is required. . O- ]6 }, z& B% q' @. c; Q; TThe 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. - J x, m- g4 q: J' X/ s2 v
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. P6 K6 k0 H0 r(2) For a given RF, frequency compensation can be optimized. 7 o2 I( v6 i7 w% B(3)Suitable for high frequency applications.; s1 t+ a4 o& r3 O6 m