Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Some questions about the attached OPAMP

Status
Not open for further replies.

taofeng

Advanced Member level 4
Joined
Mar 21, 2006
Messages
104
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,296
Activity points
2,021
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

Member level 3
Joined
Feb 13, 2007
Messages
55
Helped
5
Reputation
10
Reaction score
4
Trophy points
1,288
Activity points
1,739
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

Advanced Member level 4
Joined
Mar 21, 2006
Messages
104
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,296
Activity points
2,021
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

Member level 1
Joined
Jun 8, 2005
Messages
36
Helped
7
Reputation
14
Reaction score
1
Trophy points
1,288
Activity points
1,468
the right part is a floating-current mirror classAB amplifier
I donot know why the left part's top is connect to VOUT
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top