關於two-stage-opa unit-gain bandwidth可以多小?

robin0338

新手發問
two-stage-opa
& p( F, p! Y9 u; s8 x' P  g. c如果已知訊號頻域為100hz~50k hz左右，那如果設計unit gain bandwidth到50Mega hz以上的話，

% t; q5 x! T3 \# J1 X, G1 z是否有點浪費? 而且功耗也會多一些?
6 S% W8 y8 m/ x6 ?3 [9 h
3 ~* d! y( f6 `, i是否應該設計到unit gain bandwidth =1Mega hz  

! t7 s( ^  c8 {- F+ h-3db frequence =10k hz

1 ]% k* ?  ~& N( c6 h* @但是 two-stage-opa 的gain似乎是有極限的，那這樣頻寬是否也會造成無法縮減到1Mega hz

! l3 k6 K, _" H  _2 K想請問版上的高手  謝

tsay

bandwidth is based on the time constant.. if you have 50hz so the timing is 1/50, you can get the T. after that you can get the 3db bandwidth