Help! circuit problem!

[overmars]

Pic1 shows this circuit and Pic2 shows module D.
I don't know what module D functions. Vc is the control logic and module C determines charge or discharge M5 or M6. V+ is the reference voltage.V- is a CM feedback.

Thank you in advance.

 

[wjlzhx]

can you say more clear???
in pic1,D block has 4 inoutpin ,but in pic2 i just see 2 inoutpin.

and where is VC from ,and what is C??

 

[overmars]

I'm sorry , I just update the pictures.

pic2 is Module D that consists of module C and M1,M2,M3,M4,M5,M6.
A1,A2,Vc are the inputs and V- is the output of module D.

C is the logic circuit which determines the voltages on gates of M1 and M3.

Vc is a digital signal to enable or disable the module D.

A1 and A2 are the input currents module D.

thank you for your help.

 

[butterfish]

Your circuit should be more detail.
Does V+ connect to a reference volatge?
It seems block D is a feed back network.
block C need be more clear, seems it can not be logic circuit, how the current A1,A2 control gate M1~4? Vc is just a enable logic signal, or a control voltage?

 

[pfd001]

pic1 is unity gain buffer, D seems no use. Is it possible for D block other output pins?

 

[seanyang]

Dear overmars, I tihnk the module D is the CMF (common mode feedback) circuit.
If your want use differential out, you must add it.
If your want know detail about CMF circuit, you can see any one analog book.

thx~~

 

[butterfish]

Oh, I didn't see Vout==V-, sorry!
it's a unit gain buffer used as a regulator, Vout supplied block D.

 

[overmars]

Thank you for the replies above.
what I am curious at is the function of this module D which should have more outputs.
V- is CM feedback signal and V+ comes from reference voltage.
If there is any difference between V- and V+ , the current through A1 and A2 will be different. So it seems that module D forces to make V- and V+ as equal as possible.