Some questions about the attached OPAMP

[taofeng]

Hi,

I have several questions concerning the attached opamp structure.

1. What is function of M14, is it source follower ? how does it work ?
2. What is the function of Mp and Mn, common gate ? how does it work ?
3. Does the M16 and M17 form the class AB structure ?
4. What is advantage of this OPAMP ?
5. Is it a LDO circuit ?

thank you for your time,

taofeng

 

[arghpok]

Where did you get this circuit ?

It is definitely NOT a LDO because its output has no stable feedback and the transistor Mp (if it is the pass-transistor) is not supplying any output current. Those resistance over the left side are simply making a current mirror with the ratio you want by placing the correct value for R2.

And the the transistors M16/17 effectively form the class AB output.

 

[taofeng]

It is from an interview question.

I guess you right it is not a voltage regulator. There is no feedback from either Mp or M17 to the input differential pair stage.

I have one more question, the biasing current for current mirror is load dependent, by which I mean the current through M17, what is the advantage of this ?

regards,

 

[castrader]

the right part is a floating-current mirror classAB amplifier
I donot know why the left part's top is connect to VOUT