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77 Threads found on edaboard.com: Stage Cascode Amplifier
The assumed first order gain characteristic isn't bad as an estimation. There's an additional cascode stage pole, but you can probably ignore it. The other expressions are however only right if C2 >> Cf, otherwise the amplifier output impedance matters. As a short cut, it's rather unlikely to drive an amplifier with (...)
Hello, I am attaching here a multi-stage cascode amplifier schematic operating at very high frequency at bw of 28GHz. A part I have understood about the circuit as following From RFin signal travels through L and C matching network then from source degenerated CS stage to cascode (...)
You are comparing apples and oranges. Folded-cascode is a way to design an amplifier stage. Class AB describes the manner a power output is driven.
I am designing a stacked CMOS power amplifier using st65nm design kit. The device I am using is nsvt25_rf. While designing cs stage maximum Vdd I took was 2.5V. Can someone suggest the Vdd that should be used in cascode configuration (2.5V or 5V?). Is Vds value specified in design kit the maximum Vdd that should to given or maximum Vds (...)
I am designing a difference differential amplifier following the attached schematic. With a folded cascode first stage & Common Source as a second I am wondering how would the CMFB circuit look like? What i
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 no constraint on (...)
gain of alone CS amplifier is -GM*rd. Using the simplified transistor model assumed in your gain expression (infinite output impedance), the additional cascode stage doesn't change the gain of the basic CS stage. Your circuit however implements additional source degeneration. With Rs = 200 ohm and Rd = 100 ohm, the (...)
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 depends to feedback (...)
Adding a cascode stage in an amplifier increasing the output impedance. What the advantage of this? The main benefit of a cascade amplifier is better high frequency performance because the "Miller Effect" is eliminated. The increased output impedance might be a problem, not an advantage.
I have attached a picture of a folded cascode amplifier with class AB push pull stage. My question is regarding the SLEW time of the amplifier. During the 'internal slewing' when the compensation capacitors CM1, CM2 are being charged up, what is the status of the M4, M4C, M8A, M9A, M2C, M6 ? Do these mosfets operate in (...)
Hello, I have attached a folded cascode amplifier with class AB stage picture which is commonly seen in text books. I would like to know : * Supply VDD = 15v. On the NMOS side, the cascode nmos (M1C, M2C) are 30V devices and the bottom nmos (M5, M6 ) are only 5V devices. What is the special reason to do this ?? * (...)
Hi, I want to analyse the circuit below. It is an RF power DC mode: Assuming that Ld is ideal then there is no DC voltage drop across it. => VD2 = VDD. In the mean time, the capacitor is open at DC => no current flowing through Rb => VG2 = VD2 = VDD In A
WHat is significance of cascode amplifier? why do we use cascode amplifier?..why to use folded cascode and why is that called as folded?...
hi, i'm designing an integrated k/ka-band power amplifier with cadence virtuoso which looks similar to this one: 90974 in my case the load inductivities L1 of the cascode stage are about 100 pH. i simulated the s-parameter stabilityfactor kf. it is below 1 for a very wide frequency range from 20 GHz to 70 GHz. the m
Hello, the amplifier in the attachment is a folded cascode with class AB stage. Is there a suitable 'current limiter' circuit architecture that you can suggest ?? I need to limit the max. current to + /- 10mA
Hi all, Given a millimeter-wave multi-stage common source/cascode CMOS amplifier. Which method would be the proper design: inter-stage conjugate matching or resonance load (adjacent stage should be place close in the layout)? For CMOS transistor, it is gate-source voltage controlled device, it is more (...)
the cascode amplifier,works by changing the input signals voltage into a current in the first stage. In the second stage the signal current is changed into a voltage. The advantage of this is that as the input impedance of the second stage is very low, the signal current develops very little voltage st this (...)
Make a Telescopic cascode for the first stage for high gain of atleast 300. This would be easy. A telescopic itself would give a gain of around 1000 if designed well. Make a Regular Common source stage as second stage with a gain of atleast 10. Also easy. Put appropriate compensation for stability. You can refer (...)
Hi! I am doing a class AB common source output amplifier with a folded cascode gain stage. The load is 1pF and 10 kHz. supply is 0-5V. the gain is > 70 dB Everything was working as expexted until I changed the DC voltage of the load. When loads are grounded the phase and gain are as I expected, but as I turn up the common mode load (...)
Hi all I just have a doubt on cascode amplifier. Is it really necessary to use the same dimension device for the cascode stage transistor in a cascode amplifier. If so, what is the reason and if not what are the benefits by choosing other dimension device. One more (...)
Based on the cascode structure ,Why the cascode stage has a relatively small impact on the overall noise figure ?
... M3-M4 are working as a current buffer. what is the effect of this current buffer on the amplifier gain? Actually it's a cascode stage -- the combination of a common gate (M3-M4) and a common source stage (M5-M6). Due to higher output resistance at the common drains, this topology provides larger di
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..!!
when you had a 2 stage design, you need to set any one of the pole the dominant, so you need to add a compensation cap this would have lower phase margin. without the second stage you now have a single stage system so you will have higher phase margin.
what do you mean by second stage in ur pic? Folded cascode is single stage amplifier, though with a rather comlicated load... as for ur pic, ur input is too small: only 20uV peak to peak. The output then is acceptable since even a 60db gain would not be able to rise output voltages to opamp saturation. One thing u must (...)
Hi guys, please, somebody tell me, why is the telescopic amplifier supposed to have a superior noise performance compared to other amplifiers? Regarding the folded cascode, it's ok, we have more transistors producing noise. But, what about the ordinary 2-stage Miller amplifier?, or a simple (...)
Hi, I'm trying to design a fully differential folded cascode amplifier (2 nmos and 2pmos) with pmos input. could anybody suggest a bias circuit? I've already designed a bias circuit but the nmos transistors are in triode region. all the bias transistors are in saturation and the pmos transistors of the folded cascode stage (...)
You first have to find the node which has the lowest pole....that will be the main contributing factor towards the w3db....most probably the output of the first stage......what you can do is use a cascode amplifier for your first stage and if you have a large capacitive load you need to decouple it from your main (...)
A cascode amplifier consists of a common emitter stage feeding a common base stage. Since the common base stage has the base grounded, the AC voltage at the collector of the CE stage, as ckshivaram mentioned, is very close to zero. It is the variation of the base-emitter diode of the CB (...)
hi i feel there are 2- mistakes in the design 1) ur output stage is nmos is current source & Pmos as amplifier... this leads to large offset... u have to chenge it to Nmos as amplifier & Pmos as current source 2) the is a cap (i cant figure out the value) between drains of input differential pair NMOS transistors..instead u have (...)
I am simulating a shunt-feedback transimpedance amplifier with cascode gain stage and a source follower in AC analysis with magnitude below is my bandwidth and noise
hello everyone... i have to design a telescopic amplifier on 0.18um Spectre. my ugb requirement is 500MHz and gain > 80db , Cl=1pF .Although power diss. limit is given i decided my current be 320uA to be ok. I calculated all W,Ls according to the basic equation for SINGLE stage TELESCOPIC amplifier topology as given in Razavi on Oage (...)
HI I have designed a capacitive feedback OTA ( OTA is folded cascode single stage OTA with ideal CMFB). When I simulate the loop gain of OTA (using iprobe and stb analysis in cadence) I get a 'High Pass' response at low frequencies. I am not sure why this is happening. Please help to solve this issue. Thanks
it seems the amplifier is in open loop, how about output voltage, which would effect cascode MOS. In my view, the biasing of cascode MOS decide common source MOS status (Linear or Saturate), while output voltage effect the casode stage.
proper bias is to keep every transistor in saturation region。 try to find the poles and zero of the 2-stage amplifier. i think the book entitled analog design essentials by Sansen has elaborated the design procedures systematicly.
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 in Fig6). The AC (...)
for me design a folded cascode with only a dominating node only, so you can have a large gain but you may not need to do compensation. if still cannot meet your requirement, then do 2 stage
hi what is the use for 2nd stage(class AB,Common source,etc..) in folded cascode opamp? THanks Bhanu
Because it is one stage amplifier, compensation capacitacne is actualy the load capacitace.
Since you won't be needing a high output swing you can go for a single stage telescopic cascode differential amplifier that will give you a decent gain with good PSRR and low power consumption. The main problem with this is the systemic offset which may or may not meet your spec of BGR+10mV. Alternatively you can go for a typical (...)
My guess is that you are running into problems with M3 & M4 going into linear region rather than saturation, starving the current out of the folded stage. You can check this by verifying the current levels in each leg of the amplifier. There are a couple of things you could do to prevent this: 1- Make M15 longer channel length with very narro
Hi: I have a small question about this opamp compensation as shown below. the feedback is not shown but you can see C2 is used as the compensation cap. on the other hand, there is a RC filter (R1-C1) used at the output of the 1st stage folded-cascode amplifier. This block indeed improves the compensation result. Can any one help explain (...)
I think if you are using the two stage amplification in the CMFB amplifier, the same problem of two stage Opamp stability problems are appearing in your circuit. May be your test bench could be missing some capacitances required. Connecting the two differential outputs with two identical capacitors to the CMFB node may solve the problem and (...)
Almost no difference with NMOS diff pair. A folded cascode can be used for 1st stage of low voltage application.
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
Yes, left hand side is ... and Q1 and X0 form an AB bias control for the output stage M22 and M23. The biasing of the AB-control is by Q0 and X1. Using npn's and pnp's is favorable but requires bicmos.
Normally OTA is a one stage amplifier like a folded cascode architecture which only have one pole and OPAMP is a two stage amplifier which will have 2 poles. In terms of characteristic between 2 of them, you can refer to what others have explained. The book of Philip Allen explain well of this and the application.
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 (...)
floating current source class-AB stage will meet your requirement
i have designed a folded cascode fully differential opamp used for pipelined adc(1.5 bit per stage),but there are some problems: when i test it in open loop with ideal cmfb(vcvs source),the GBW is 103M,dc gain is 80 db,-3db bandwidth is about 10khz;however,when i test it in closed loop with sc-cmfb,there are some strange problems: first,my design