Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics 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.

Question aboout switched-capacitor CMFB in switched-cap amp

Status
Not open for further replies.

neoflash

Advanced Member level 1
Joined
Jul 2, 2005
Messages
492
Helped
10
Reputation
20
Reaction score
2
Trophy points
1,298
Activity points
4,759
Feel a little difficult to derive the linear model for the switched-capacitor CMFB circuits.

Any suggestions or recommended tutorials.
 

neoflash

Advanced Member level 1
Joined
Jul 2, 2005
Messages
492
Helped
10
Reputation
20
Reaction score
2
Trophy points
1,298
Activity points
4,759
Another question is that CMFB refreshing phase (phi-2) should be in the same time of integrator sampling or integration?

I guess doing the refreshing in integration phase make more sense, right?
 

arunkumar446

Full Member level 3
Joined
Jul 9, 2008
Messages
168
Helped
6
Reputation
12
Reaction score
3
Trophy points
1,298
Activity points
2,198
Re: Question aboout switched-capacitor CMFB in switched-cap

where ever you got this pic. i think that is a good reference. i guess it is from "Analysis of Switched-Capacitor Common-Mode Feedback Circuit" by Ojas Choksi.
This paper is a very good reference.

Added after 2 minutes:

refreshing in the integration phase makes sense, me too think so.
 

BackerShu

Member level 3
Joined
Dec 22, 2007
Messages
57
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Location
USA
Activity points
1,795
Re: Question aboout switched-capacitor CMFB in switched-cap

neoflash said:
Feel a little difficult to derive the linear model for the switched-capacitor CMFB circuits.quote]
What do you mean by ''linear model''? Isn't the model proposed in the paper suitable?
 

neoflash

Advanced Member level 1
Joined
Jul 2, 2005
Messages
492
Helped
10
Reputation
20
Reaction score
2
Trophy points
1,298
Activity points
4,759
I realized that it doesn't matter which phase to refresh the cmfb. Becasue the input CM is not allowed to jump a lot during successive clock cycles, otherwise, the circuit can't work anyway.
 

yschuang

Full Member level 3
Joined
Feb 1, 2004
Messages
183
Helped
15
Reputation
30
Reaction score
2
Trophy points
1,298
Activity points
1,002
Re: Question aboout switched-capacitor CMFB in switched-cap

Hello, neoflash

You explained the size of C1 and C2. If the size of C1 and C2 is wrong, input common mode voltage jumps and then settles.
 

arunkumar446

Full Member level 3
Joined
Jul 9, 2008
Messages
168
Helped
6
Reputation
12
Reaction score
3
Trophy points
1,298
Activity points
2,198
Re: Question aboout switched-capacitor CMFB in switched-cap

hi guys what ever i try the capacitance values the output for a constant input is oscillating can any body help me with this issue. Thanks in advance. i need just a fully functioning circuit for the SC-CMFB to know and do a circuit like that.it's urgent guys please reply asap.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top