slide 1010 ) a# x. R0 l9 X! n 6 \; Z, `# `: Q4 V0 ]For a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. : C$ \: n) L. {; S% G. o% i- y- K
The signal bandwidth is determined by RF and not by the circuit gain. 9 v% N S3 b" ?& }8 ]8 ZThe circuit gain is independently set with RS.7 b/ S4 ]) u. H9 k8 F
The signal bandwidth remains stable for all gain settings ./ j5 x. P( I* w i$ g q
Even for unity-gain operation, an RF resistor is required. 0 y8 ?+ U' ]1 z- Z# Z6 kThe 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.2 m5 j4 s6 `, l0 m" h
slide 1020 , l3 {% B9 y% ?) K/ W ) p% u( L% J4 _2 |5 B(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. , W" N0 K" c' o(2) For a given RF, frequency compensation can be optimized.! E4 e2 ]# h( N( M) t
(3)Suitable for high frequency applications.3 Q _# b7 L, t
slide 218 ' t A% I2 S' G9 q, f( I6 j5 L1. First order Sigma-Delta patterns in the output spectrum; a7 R# Z4 Y3 Y8 I8 T
=> Idle tones(pattern noise, limit cycles) ; N+ h: i1 B0 l& e0 F2. Second order Sigma-delta 輸入太大時還是會不穩定