How to decide on the OP specifications needed for a design?

[ilter]

Dear all,

I have a question. In analog circuit, op is important.
Switching regulator and LDO need error amplifier.
ADC needs op. How do I calculator or need which kind of op?
Like op spec. , gain 、 BW 、CL(output cap) or slew rate?
Maybe gain=60 dB or BW = 30M at CL=1u?
How do I decide my op's spec. ?
Thanks.

 

[libinphy]

OP design

It is determined by the specification.If the OP_AMP is not satisfy your specification,please change it.there is not a standar rule to select OP_AMP

 

[rose_song]

Re: OP design

you can calculation the opamp' parameter base on some spec requiments.

 

[cinch]

Re: OP design

Hi,
Selection of opamp architecture is purely based on spec. There is lot of difference between the opamp used in power management and that used in data converters.

If u need an opamp to drive high capacitive load with good gain, go for folded cascode, since it has a property of better phase margins at higher load. But this comes with a trade off of lesser output voltage swing. If u want moderate gain with good bandwidth, go for simple miller cap compensated opamp.

In most of the cases, single stage folded cascode opamp serves the purpose.

Regards,
cinch