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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. 9 g9 \" g" y |/ h
The signal bandwidth is determined by RF and not by the circuit gain.! B, ]( D& o$ h- N, g' @
The circuit gain is independently set with RS. : c! Y: F) K6 C( _The signal bandwidth remains stable for all gain settings . + X6 G6 m/ \" gEven for unity-gain operation, an RF resistor is required.5 ?$ v9 Z- n5 D- ]4 D0 d
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.; x3 F' o. E5 N7 q
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(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. x) K2 z" v4 ^0 Z. q6 [3 b(2) For a given RF, frequency compensation can be optimized.% N/ }# @4 r0 s6 V) }8 @
(3)Suitable for high frequency applications. + g: A5 ^) y$ B' a0 i# K
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1. First order Sigma-Delta patterns in the output spectrum0 K, E9 b9 ?# N7 s+ S* F* e
=> Idle tones(pattern noise, limit cycles) 7 U1 H8 `2 B. J- L2. Second order Sigma-delta 輸入太大時還是會不穩定