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61 Threads found on Capacitor Cmfb
Hi guys, I want to design a full-differential two-stage OPA. The first stage is telescope cascode structure and the second on is usual common source structure. I want to use switched-capacitor cmfb to make the output common-mode voltage stable. I am wondering now that how many SC-cmfbs I should add in the OPA. One SC-cmfb (...)
Hello everyone, I'd'like to design a switched capacitor amplifier 94797, But I don't know how does this amplifer work. Here is my own point of view: in the S1 phase, the circuit in the sampling phase, VCM and LM49 supply a cmfb; in the S2 phase , the circuit is amplified stage. However when I use the spectre simulation
Dear all I am designing a differential folded cascode ota and using a sc-cmfb. My problem is about selection of the capacitor ratios. Suppose C2 is directly connected to the output node of the ota, and c1 is pre-charged to the difference between the biasing voltages Vcm-ref and Vbias. I have seen in the book of k.martin is that c2 should be appr
I am using a sc cmfb for the fully differential telescopic OTA. on one phase my output is auto zeroed or connected to agnd and on another the input is sampled and amplified. on the phase in which the input is sampled and multiplied, the output common mode doesnt seem to remain constant with sc cmfb circuit. i have kept the rise and fall time as 1n
hello friends I have designed the folded cascode opamp...(fully-differential)....i have added SC-cmfb circuit to Amplifier ....but i am getting problem in simulating with PSS and PAC analysis.. my detailed steps for the analysis are as follows... set pss simulation for clock of 2.56MHz and input signal of 256K
thanx I am not use cmfb simply Folded Cascode Input and Common Source Output Stage with 4 pf load capacitor my gain is 73 db. Now what is the error ? cmfb is require ? now I want to design 4.3MHz LPF using these opamp but it is not working can you solve these problem.
Hello, my friend. Maybe this paper will help you. Please see it. Analysis of Switched-capacitor Common-Mode Feedback Circuit Ojas Choksi, Member, IEEE, and L. Richard Carley, Fellow, IEEE IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: ANALOG AND DIGITAL SIGNAL PROCESSING, VOL. 50, NO. 12, DECEMBER 2003
A question to think about. 1) Yes it seems to me too from the circuit that the cmfb loop has a positive feedback. 2) CM feedforward: This is a common mode feedforward. I think the capacitor averager is used for compensating the cmfb loop by accomplishing this feedforward technique. 3) The series RC circuit introduces a zero to the (...)
i have designed a two stage fully differential opamp with hybrid ahuja compensation (that is, two compensation capacitor used in the two cascode nodes of each branch), the first stage is folded cascode, the second is common source, and the cmfb is continuous common mode feedback which have two input pairs, one pair connected to vcm, the other pair
Hi, all Somebody in this forum said that, the OTA with S/C cmfb simulation could be done by PSS, PAC...., with spectreRF, but could anyone explain the detailed procedue or just give me some documents on that? I need it badly now! thanks a lot, and best regards Added after 5 hours 17 minutes: I tried t
Hi, all, I am designing a switched-capacitor S/H circuit, and from some documents, I found that the opamp used in the circuit takes use of a switched-capacitor cmfb, what I want to know is that, why this specific cmfb should be used here, but not a general cmfb circuit? and also any literature about (...)
HI, anybody has some good ideas to simulate the AC characteristics of the differential opamp with switched capacitor cmfb circuit? Because the switched capacitor has no DC operating point, so how to deal with it in AC analysis? thanks.
Hello, can anybody comment on what is the best way to measure/simulate the switched capacitor cmfb circuit?
I dont's know How to simulate switch-capacitor using ac analysis with spectre. such as , fully differential opamp with switch-capacitor cmfb. Can you give me some suggestions. Thank you.
then you are going to use it in Switched mode. Then you can use SC-cmfb, which is better in performance compared to other cmfb's. You can refet to this paper Analysis of Switched-capacitor common-mode feedback circuit by choksi, carley
Feel a little difficult to derive the linear model for the switched-capacitor cmfb circuits. Any suggestions or recommended tutorials.
for a fully differential opamp, SC-cmfb is commonly used. if Gain-Boosted telescopic opamp is used, then both main opamp and auxiliary amplifier need SC-cmfb circuit. i want to ask: how to choose the value of the two cmfb capacitors C1 and C2 (assume C2 is cmfb capacitor) for both main (...)
for a fully differential folded cascode opamp, the sc-cmfb circuit is used. i want to know how to calculate the CM-GBW and how to calculate the CM feedback factor FCM? the following figure is the simplified sc-cmfb half circuit, Cg is the NMOS tail transistor gate parasitic capacitor, FCM=C2/(C2+Cg) or F[size=2
Hi I`m desing a rail to rail folded cascode Op amp I have some question in Fully diff Amp 1: How to modeling the ideal SC cmfb Now I using the resistor and capacitor cmfb 2: How to simulation the Fully diff amp ICMR , SR Textbook(allen) describe thd single ended amp
1) DNL is affected due to comparator offsets and due to gain error of the opamps in the mdac sections. the INL is just a cumulative sum of the DNL. the SNR, THD are frequency content parameters. the finite gain and bandwidth of the ota in the mdacs, the bottom plate capacitances, the error in capacitor values and many more will have a toll on t