! ?7 y- e) H& R# dFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. ( n1 A8 ~3 a% }6 r+ `8 \
The signal bandwidth is determined by RF and not by the circuit gain. 2 g" l: \( P1 k p! dThe circuit gain is independently set with RS. 6 u2 [. U9 z4 B, @& l, i# AThe signal bandwidth remains stable for all gain settings . / N5 c0 M; ]8 g: p8 HEven for unity-gain operation, an RF resistor is required. ! P9 F! H- [8 P4 y! A& jThe 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.+ V; n* v/ Z% |! }2 O' F1 Z
slide 1020 ( G( y1 s2 q/ [ / M4 D4 C. l9 ^, E' t(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. ' p( K0 b) {0 k# M* D* M(2) For a given RF, frequency compensation can be optimized.! o, L0 K: u+ N* @7 u
(3)Suitable for high frequency applications. 0 G8 z9 B y6 U3 L, ~! \: s1 |9 z
slide 218 ( u3 {3 `- b/ |9 ^) |1. First order Sigma-Delta patterns in the output spectrum& Q+ o, F, T; p/ G% v
=> Idle tones(pattern noise, limit cycles)7 I: M! c$ x2 U5 |- z! \9 Z
2. Second order Sigma-delta 輸入太大時還是會不穩定