Relation between slew rate and minimum closed loop gain

[aarthy_maya]

Hi all,


I am looking for the relation between the minimum closed loop gain and slew rate?? can someone help??



Thanks!
Aarthy

 

[FvM]

There's no relation. Slew rate is basically a large-signal parameter, related to non-linear OP behaviour. In a classical miller compensated OP topology, it's set by the current of the first stage and the miller capacitance.

 

[aarthy_maya]

Hi FvM,

the reference
"http://books.google.com.sg/books?id=V-N4jbgbo9sC&pg=PA84&lpg=PA84&dq=feedforward+compensation+in+operational+amplifier&source=bl&ots=lQTpe6aLmd&sig=JHHu8IhnhEmzpgxhVArzgcmcXD0&hl=en&sa=X&ei=C-qET-_6KozPrQfOtrSxBg&ved=0CDMQ6AEwAg#v=onepage&q&f=false" on page 4 (i have attached the same for sake of easy)

states that there is a relation between them, but never mention what is the relation



That is why I am looking whether there is real direct/indirect relation or it is a false statement

Thanks!
Aarthy

 

[FvM]

There's a relation when designing the OP. Changing the compensation affects both. Many other OP parameters are mutual dependent as well, that's what the literature is talking about.

Your question makes sense if you consider a specific unity gain (miller) compensated OP. You may want to have a decompensated version of it. Keeping all design parameters, except for a reduced miller capacitance. For several commercially available OPs, you'll get such a decompensated version. They have increased slew rate and gain-bandwidth product, and also an increased minimal closed loop gain of e.g. 5 or 10 in return. LF357 versus LF356 is a classical OP I remember in this regard.

 

[aarthy_maya]

Hi FvM,

Thanks for the reply! I understand it now.