question about heavy load amplifier compensation structure

[Leo@27]

I'm wondering if there exists a way other than the traditional Miller compensation to compensate a classAB output stage opamp.

I ask this because when driving a large capacitive load, the capacitance used for compensation also increases and is very difficult to integrate it on chip. I need the classAB to provide rail-to-rail output range, and the gain of the second stage op-amp is sufficient for my design, but the capacitive load requirement makes traditional on-chip compensation unusable.

Here's my question: what frequency compensation architecture is typically used when driving an 100s nF- or even uF-rated capacitor? Is it possible that a 3-stage op amp is more viable in this case, as opposed to a 2-stage op amp? Could anyone answer my question please?

 

[nitishn5]

Why can't you make your output (load) pole the dominant pole? I.e. do a Dominant pole compensation

 

[Leo@27]

Why can't you make your output (load) pole the dominant pole? I.e. do a Dominant pole compensation

Hi nitishn5，

thanks for your answer.

Because I also need the rail-to-rail output range, i don't think amplifier's wide output range could coexist with high dc gain.

 

[D.A.(Tony)Stewart]

Can you include current feedback?

--- Updated Jan 17, 2024 ---

2nd stage compensastion

https://vtechworks.lib.vt.edu/server/api/core/bitstreams/f75d6e84-e53f-4cff-aa25-7e52667265f7/content

 

[Leo@27]

Can you include current feedback?

--- Updated Jan 17, 2024 ---

2nd stage compensastion

https://vtechworks.lib.vt.edu/server/api/core/bitstreams/f75d6e84-e53f-4cff-aa25-7e52667265f7/content

Hi Stewart,

No I can't, When using a current buffer, the size of the compensation capacitor is proportional to the root of the load capacitance . This structure is also clearly impractical when driving 10nFs capacitors. Because you may need hundreds of pF compensation capacitor.