Continue to Site

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.

Register Log in

a question with differential amp and cmfb

Status
Not open for further replies.
W

wdd

Member level 3
Member level 3
Joined
Nov 12, 2004
Messages
66
Helped
8
Reputation
16
Reaction score
1
Trophy points
1,288
Activity points
510
hello, guys,
I have designed a diff amp with SC-cmfb, the phase margin need to be opitimized,
when i do ac simulation, the SC-cmfb should be took out, so my question is whether the capacitor in SC-cmfb be one part of Cload??
thanks a lot.
B&R
 

wdd said:
hello, guys,
I have designed a diff amp with SC-cmfb, the phase margin need to be opitimized,
when i do ac simulation, the SC-cmfb should be took out, so my question is whether the capacitor in SC-cmfb be one part of Cload??
thanks a lot.
B&R
Click to expand...

Yes, because SC-cmfb introduce some loading effect to your diff amp. Actually SC-cmfb is a kind of switching load, which is not purely capacitive, its effect to your amp also depends on the switching frequency.
 

    W

    wdd

    Points: 2
    Helpful Answer Positive Rating
thx hylas,
do you have some papers or document relevant?

B&R
 

I don't have any references. But you may try in this way:

Assume the switching frequency of the SC-cmfb is much larger than the bandwidth of your amp. Eg. fsw > 10*UGF
1) Obtain a low frequency model of the input impedance of your SC-cmfb circuit. Input of the SC-cmfb circuit should looks like a resistive element at low frequency.
2) add the equivalent resistance to your amplifier and see the freq response.

Hope this help.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top