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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. # |% i% e3 a/ Z% U8 pThe signal bandwidth is determined by RF and not by the circuit gain.) i2 I* L9 d8 G' K4 h1 {
The circuit gain is independently set with RS." N+ N8 ]7 Q' \+ E0 s3 n" H, V
The signal bandwidth remains stable for all gain settings . # Z% D& J4 ~" P/ P C! P. ~Even for unity-gain operation, an RF resistor is required. ) Q" |2 r# i0 e4 x" U i BThe 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 D: V( G; u4 T7 O( ?! v( O( Y
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. 1 @' _1 t% x: D) ^(2) For a given RF, frequency compensation can be optimized. 6 I5 O- B7 J3 m+ j(3)Suitable for high frequency applications. # }0 ^! W( V/ n. F4 a
slide 218 6 g. G6 N2 d$ W# ?' a, y' X1. First order Sigma-Delta patterns in the output spectrum! ]2 {! E1 R0 n/ V+ @
=> Idle tones(pattern noise, limit cycles)& i1 w B9 Q) h; B5 k9 j0 D
2. Second order Sigma-delta 輸入太大時還是會不穩定