slide 1010 1 B# Z" B( s$ I3 c( ~4 j + F4 }/ p: N" k& a! y# K- |5 UFor a CFB amplifier the open-loop gain is ZT and its feedback factor is 1/RF, making the loop-gain TCFB = ZT/RF. ) H$ n/ d7 N+ |$ V
The signal bandwidth is determined by RF and not by the circuit gain. ! u# L* F; e! U) y/ D- LThe circuit gain is independently set with RS.8 t; P3 J0 Z6 g" F
The signal bandwidth remains stable for all gain settings . # @, K6 t7 K1 J! uEven for unity-gain operation, an RF resistor is required. $ ^& w) z) z6 U! u* J( l' n4 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.* L$ R& b0 M% Z* _* ?+ m/ T2 i
slide 1020 # O6 q' B T" v3 g; {+ ~8 n8 V 0 f5 u$ i+ e& v( P(1) The closed-loop gain can be modified by changing RS, leaving the closed-loop bandwidth unchanged. ) t, @. M% ^9 K0 h% L2 |0 x% y(2) For a given RF, frequency compensation can be optimized.5 |+ ]" Q3 E3 ~ u& ^
(3)Suitable for high frequency applications. ; V# U: s5 t( M+ u1 n