slide 1010 + d% @* s' }$ I! f1 l+ `7 b( l2 N$ i
For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. ' E; t0 e* m6 r0 P6 W0 G- qThe signal bandwidth is determined by RF and not by the circuit gain.$ M" Y. }0 X& ?$ O: e* n6 o5 {
The circuit gain is independently set with RS. 5 v ^$ i4 Y6 M& @7 Z7 vThe signal bandwidth remains stable for all gain settings . x8 p( c% \- w. `* u
Even for unity-gain operation, an RF resistor is required.8 h7 P: t( y& |0 n1 G8 u
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." h% ~5 U1 c: C
6 l) |/ n& b0 o! c3 W(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged., f0 G( @% x1 n$ n7 K7 F7 w
(2) For a given RF, frequency compensation can be optimized. 8 }5 @* Q/ H! A(3)Suitable for high frequency applications.0 Y' p* p/ Q2 W1 W/ v2 d$ N
slide 218 1 z8 p% v* e; b1. First order Sigma-Delta patterns in the output spectrum5 i7 a. p6 U w
=> Idle tones(pattern noise, limit cycles)0 ^- q7 {- }% A/ k0 i: E
2. Second order Sigma-delta 輸入太大時還是會不穩定