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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. 1 a. N% A( T# p; c
The signal bandwidth is determined by RF and not by the circuit gain. / r4 \% c v; a1 }1 w* NThe circuit gain is independently set with RS., x; L; A# T0 l4 |* |) T( p; n3 i0 E
The signal bandwidth remains stable for all gain settings . + x+ G' C) @8 k. m! Y" `$ o$ _6 j lEven for unity-gain operation, an RF resistor is required. 4 P2 U* H$ r" E1 B3 oThe 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/ k" l* c
* K" T: B1 x0 I(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. G) W/ X$ p# T" S" H
(2) For a given RF, frequency compensation can be optimized. , J5 z0 X0 N7 F7 T5 w' d i/ ~* w, g(3)Suitable for high frequency applications.9 ]$ Y: |4 s# X( E4 F
slide 218 , u7 L' i2 F. @- J2 b5 u1. First order Sigma-Delta patterns in the output spectrum" C3 N* _/ W" [( }0 G
=> Idle tones(pattern noise, limit cycles) 3 M) E" n+ f; R2. Second order Sigma-delta 輸入太大時還是會不穩定