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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. 0 O( I2 o. i5 @
The signal bandwidth is determined by RF and not by the circuit gain. - X* L8 B& J7 R& [6 J1 m6 IThe circuit gain is independently set with RS.9 m0 P' U1 k W
The signal bandwidth remains stable for all gain settings . + U0 {1 F0 G/ h9 w5 A! T3 hEven for unity-gain operation, an RF resistor is required.6 p. K' [ E, \9 \9 z
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.9 R; ]0 x2 L+ U0 X
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged.. `/ [3 s; b. S0 m/ G
(2) For a given RF, frequency compensation can be optimized.# o" r y- c7 }' W# r1 |! k; P
(3)Suitable for high frequency applications.0 w. |: C( T$ y2 `0 _ k @