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89 Threads found on Two Stage Cascode
Hello friends I need to have a high-gain amplifier circuit with pmos input. Who can help me?
So with regards to M8 and M9, that is the current sink of input stage. M10-M12 is the bias network for the second stage output(M13 and M14), to allow it to go rail to rail. Addressing R3, I haven't seen this technique before but I would guess that the purpose of R3 is to match the currents between the two branches. If one (...)
i have designed two stage fully differential OPAMP. i have theoretically calculated output swing, it is coming 172mV to 945mV. power supply is 1.2V in 65nm technology. for checking in voltage swing in simulation i have connected it like a buffer and input sweeped fron 0 to vdd. but output is not tracking input at all. i m attaching plots. plz tell
two stage opamps are normally used to enhance the gain of opamp as one stage can not provide high gain. However, there is a compromise, higher the number of stages, higher the number of parasitic poles, Therefore, it is more difficult to stabilize the opamp and to have wider unity gain bandwidth. Folded casocode single (...)
Hi guys I have made a two stage opamp with pmos differential input and CS stage for the second stage in .18u technology. I got a GBW of 800MHz and I am trying to get near 3GHz. Equation says GBW=gm/Cc and despite increasing gm to even 2mA/V the GBW does not increase further. Any advice on how to increase the GBW. There is (...)
Hey guys! Desperately need help regarding a design assignment. I should use a fully differential, two-stage opamp of 0.35um technology and Vdd 3.3V. The specifications to be met are UGB>600 Mhz, P.M = 60deg and Settling time < 20 ns. I have read several research papers, but most of them deal with increasin
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 (...)
Hi, I have designed a folded cascode two stage opamp on 130nm process. The opamp works fine. Figure below shows the gain and phase response of opamp. It has 45 degree phase margin. Now the next step is to design circuit which generated the bias voltages for opamp. For initial case i used a resistive voltage divider to generate bias (...)
When You designing two stage ota, the first of all You need to add a compensation network (e.g. Miller cap with nulling resistor or used a cascode compensation). Your amplifier is unbalanced - output transistor should be matched with first stage current mirror load. In addition the phase margin and GBW (...)
Could anyone give some explanations on the effect of load capacitance on the two-stage cascode compensated OTA design. What's the influence of Cload on the choice of compensation capacitor value and GBW , PM etc.? If Cload is too large or too small, what's the difference? thanks a lot!
hi every one i am designing sar adc 26 Mhz and design input buffer as two stage ota with folded cascode as a core i wanna make my buffer switchable which work in the sampling phase and be off the rest of the clock to save power how can i make it ? can i switch on vdd i.e connect vdd in sampling and disconnect in the rest clock (...)
Tnx a lot "artmalik" I wanna design two stage folded cascode(the first stage is folded & the second is common source)but it is typical 2 stage. There are many books which can explain this. the above paper has a simple analysis for the op-amp
I'm going to design a two stage folded cascode OTA. first stage is folded cascode(nmos input pair) to provide gain second stage is common source to increase the output range compensation is cascode compensation My question is in my circuit, how to find poles and (...)
Hi everyone What is the range of Gain, Output Swing, Speed, Power dissipation and Noise in Telescopic, Folded cascode, two stage and Gain Boosted topologies of operational amplifiers? or suggest me where to find there ranges. its very urgent. kindly reply to this post. Thanks in advance.
usually you can get around 80 dB for a two stage. maximize length where possible. otherwise, use cascode stages.
I want to connect between two stage PGA that the overall gain equal i have designed the first stage by telescopic cascode op amp and feedback resistor loop on it SO how i connect between them or any one can give me any materials that talk about this problem..!!
Hi, With only 5uA current, I believe your bandgap wont drive large RES/CAP load. So either two stage miller opamp or folded cascode opamp should be OK Come on! Design it first.
Hi,there Recently I have seen a folded-cascode amp with a different input stage than usual in a folding ADC,as can be seen in fig attached. The Va and Vb are two signals from previous flash-like pre-amp stage which generate some cross zeros and amplify the different between input and ref. .I wonder what the effect of the (...)
I will assume that you have a power supply high enough to have 5 transistors stacked (one current source, two for cascoded input and two for cascoded load). If you want to reduce your UGB you need to add more output impedance or increase the transconductance of your input stage. You can achieve this in (...)
I am trying to design an op-amp with rail to rail inputs and am finding an issue with the symmetric input stage trick. I am limited to a process with no floating gate and nothing fancy like triple well. I have tried two approaches, one with a simple dual (symmetric) nmos and pmos differential pair and also with a dual folded cascode (...)
I am designing a two stage folded cascode opamp, but when I did the testing of CMRR, I found the result is not enough for my requirement. I use monte carlo to simulate it. Process&Mismatch I found that only select Process the result is fine. But with Mismatch, the result is not good. How to increase the CMRR? Can anybody give me some (...)
Hi guys, The op-amp I am working on is used to sense changes in very small capacitance(femtofarads). To get a predefined sensitivity, the input capacitance of the op-amp is limited to 1pF. I tried the usual topologies like two-stage miller op-amp, folded cascode, telescopic cascode etc. For all the cases I am able to (...)
i have designed a two stage opamp (used for a buffer, fck=15M, CL=12pF), the first stage is folded cascode, the second is common source, and i use cascode compensation to ensure frequency stability, now, i get the following simulation curve, when the input signal from 0.4 to 1.6, it settles well, but when (...)
Hi all, (1) I have designed folded cascode Op Amp with class AB output stage based on flip voltage follower (see attachment). When I added regulated differential gain amplifiers to increase the gain, I noticed that the current in PM28 and M7 are not equal (96uA vs. 91uA). When there is no gain enhancement scheme applied, those two (...)
in two stage opamp, such as telescopic + common source (as the figure shows), or folded cascode + common source, with cascode or improved cascode compensation, how to improve the PM of the opamp? first, how to decide the bias voltage for the opamp? assuming that the operating frequency is 20M, and CL=5pF, (...)
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 (...)
Hi dedalus, Thank you for your post. Actually the drain of the pmos input stage IS (not ARE) connected to the nodes between drains and sources of the BOTTOM nmos cascode. The first stage has its own current mirror load. It's two stages for sure. From what you say, it looks like a folded (...)
i have designed a two stage opamp with cascode compensation, the following is the circuit diagram, and the design specs are as follows: clock rate:12MHz CL:500fF ~ 4pF Av>90dB CMIN:0~2.2V (Vth0 = 0.7V) output swing:0.1~2.2V power consumption:as small as possible in my design, the power supply vdd is 3.3V (+-10%), Ca=Cb=800fF, (...)
I want to design an OTA for SH circuit in Pipelined ADC and some of the important specicications are, Vdd=1.2V VCMI=VCMO=0.5V Adc>96dB GBW>400MHz SR>300V/us CL=Cc=5pF(for low-noise) The two stage folded-cascode gain-boosting OTA with hybrid cascode compensation is chosen to meet the spec(the circuit woul be given (...)
i want to design a two stage opamp with cascode compensation, just as the picture below shows. i use the capcitor Cc for compensation between node A and C, my question is, how to choose the value of Cc? You can read Page305 of "design of analog CMOS integrated circuits" written by Razavi. this is a more effective co
i want to design a two-stage opamp with cascode compensation ,and the first stage is folded cascode structure, the requirements as follows: resolution:11 bit clock speed: 20M CL=2pF,Cs=Cf=1pF,DR=70dB,Vdd=3.3V,output swing= +/-1V then how to design the two-stage opamp (...)
hi what is the use for 2nd stage(class AB,Common source,etc..) in folded cascode opamp? THanks Bhanu
Hi all, I am designing a two stage folded cascode opamp. Specification of load capacitor has very high range. The minimum load cap is 470pF and maximum is 100nF. I am finding it difficult to compensate this opamp. With 470pF load capacitor, the output node becomes second pole and a miller cap will help to compensate this. But with 100nF (...)
Hello friends... Is anyone aware of this architecture composite cascode OTA..(Actually i'm using two stage with first stage as composite cascode and 2nd stage as common source stage..) I want to design it ..but lil confused how to start the design... my requirements (...)
hi, I try to design fully differential folded cascode amplifier, but have problems with CMFB stability (see attached circuit). There is too much phase shift in CMFB path (260 degrees!), but I not know where it is from!! And magnitude response of CMFB path is 80dB!! I think because of 40dB gain from cmfb amplifier, and then folded cascode output
Dear All I have a standard two stage standard OTA, first stage is folded cascode, output of first stage is given to gate of NMOS transistor with PMOS current source on top. I am using Switched CMFB to adjust the voltage at the gate of first stage PMOS current sources. I would like (...)
Folded cascode will have lower input voltage range for PMOS input but consume the largest current. Telescopic output range is very limited. two-stage will contribute more poles.
Can anyone tell me the tradeoffs between the two-stage opamp, folded and telescopic cascode topology?
how to analyze the ac and dc characteristics of opamp(cascode or two-stage) and bandgap(PTAT)? which aspects do the ac and dc characteristics contain? how to analyze them in general?
I am going to design a CMFB in two stage folded cascode differential opamp. according to the , somebody said "we need to have two cmfb circuit in two stage." is it correct that two cmfb circuit is needed in two stage folded (...)
Hi friends, I am starting to design a folded-cascode fully differential amplifier OTA with CMFB. I am confused and don't know how to start because of the large number of mosfets. I know that the ideal flow is to start with hand analysis then move to the simulation stage, but I have two problems with hand-analysis, first is the
The LM13700 series consists of two current controlled operational transconductance amplifiers (OTA) each having differential inputs and a push-pull output. The LM13700 is like a standard op-amp: both have a pair of differential inputs and a single output, but an OTA is voltage in and current out rather than voltage in and voltage out; and OTAs are
Dear all My PA is two stage Class AB power amplifier, which target ClassAB output 15dBm with 1.8V power supply @900MHz。 The structure is as following: power stage: structure:cascode ClassAB input power:5dBm power gain:10dB (...)
The tail current of the input diff pair should be larger than the sum of currents created by the two PMOS of the folded cascode stage minus tha NMOS currents. That rest current goes trough the transistor with its gate to vcmp. Since the gate is fixed, Vgs makes the source of that transistor fix too. In that way, the common node of the diff (...)
two stage,telescopic,folded cascode...especially two stage is needed... the former reports on this forum are all fully differential, I need a simpler single ened output design...THX, all
Generally, the two stage opamp maybe need compensation, because it has two high-impedance nodes as naalald said, and the folded cascode opamp does not , may be the book written by W.Sansen will be better for you to study
I believe you can easily design a folded cascode opamp with a gain of more than 70dB. Create a two stage opamp, which are folded cascode as a first stage and followed by another common source stage which will total up your gain up to 80dB. So, you no need to worry on the compensation as it (...)
1st stage is a two stage OTA
Hi, Why 3 stage? It's compensation is not easy to handle. I suggest two stage with a folded cascode in the first stage for it's input CM. If you hadn't need the 1.3 V output swing you could have reached the specs (e.g. the easy 60dB gain) with only one stage.
Hi guys, I am designing a two stage differntial opamp and i need to get a swing of 0.8 V using 1.8V supply. I have to compenstate the opamp. I am not quite sure what is cascode miller compensation using a CG amplifier. Can somebody please clearify that? I have to also use CMFB. Im not sure if i can use one CMFB for the (...)