Building fast settling OPAMPs

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DaBiz

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If you have a OPAMP that has to settle to 0.01% in 2uSec, what is best let it slew or let it go small signal
 

If you take fast OPAMP and slow it down you will get what you need - like Video OPAMP.
The OPA355 = 0.02% IN ≈50ns
Regards
Moda
 

phase margin should larger than 60 degree in practical design instead of 45 degree written in books.
 

Thanks for the information but more what I was looking for was if you have 2uSec to allow an OPAMP to settle, do you allow 1uSec to let it slew to it final value then 1uSec in small signal or 0.5uSec large signal 1.5uSec small signal or what ever. Then knowing the load capacitance your are trying to drive you set the slew rate and bandwidth of the OPAMP.
 

maybe your requiremnet is a liittle high, and it lose too much power.
 

I think there wil be large power dissipation if you use the slew rate to implement.

But there will be large bandwidth if you use the small signal to implement.

For a system, the power dissapation and bandwidth requriement is line with.

So, you can selecte either.
 

Here is a paper that would tell u about opamp settelling.
.01% is very accurate setteling. Your pole-zero location would have a dramatic effect on setteling time.
Avoid any pole-zero doublet as it spoils the phase margin and delays setteling.
hope it helps
 

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