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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. . Z/ b/ _# D: Q
The signal bandwidth is determined by RF and not by the circuit gain. - l9 @9 ` {2 ?$ GThe circuit gain is independently set with RS. % L. U8 y, B+ L N9 @" w2 GThe signal bandwidth remains stable for all gain settings .4 \5 [( I7 p. k- z/ L% u3 [
Even for unity-gain operation, an RF resistor is required. ; W- S( `9 J2 l. O- hThe 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. # H( M) }. ~3 V2 x% ?) K2 A0 X
0 D$ O4 B. D: P" a' @6 z, \* L(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged.6 S9 D( d! z* L/ Z; H9 D
(2) For a given RF, frequency compensation can be optimized. ' ?& D. p' s1 s1 t. y3 q( Q(3)Suitable for high frequency applications.+ i) V ?+ B7 F+ R0 ^
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1. First order Sigma-Delta patterns in the output spectrum$ {5 N8 M3 y9 `$ q) v
=> Idle tones(pattern noise, limit cycles) 4 C) m- c' g+ o/ F2. Second order Sigma-delta 輸入太大時還是會不穩定