8 ] r5 f" \9 RFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. & }- d0 j* h" y! kThe signal bandwidth is determined by RF and not by the circuit gain. U H* W8 ^! AThe circuit gain is independently set with RS. ; ]" a5 m6 ]+ N5 k- iThe signal bandwidth remains stable for all gain settings .! m: Q/ k6 l# A
Even for unity-gain operation, an RF resistor is required.* r, S! g- H! y, m5 E1 b2 N. C
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. * O4 w% o& D) }; w) U1 J0 _6 l5 H
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 2 v: t) h5 i) L# ?( A+ q1 ^' l(2) For a given RF, frequency compensation can be optimized. ) p: e, B H3 X, F* \! T; F; k(3)Suitable for high frequency applications. 8 V, k0 H: z. i, _6 B