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# Inversion Region

75 Threads found on edaboard.com: Inversion Region

## [Moved]: How do you make the cirucit operating in weak inversion region?

I have this oscillator design and it says it operating at weak inversion region. How do you do that? I thought Vgs controls everything whether something in saturation, triode or weak inversion but the block diagram doesn't show Vgs how it could make the device in weak inversion region as opposed to other (...)

## strong inversion region of mos

How to find the strong inversion region of a mosfet? In th book, I find, wenn gm/Id is smaller than 10S/A, is it in strong inversion region. Is it always the same for different process? Yes. In this case the inversion Coefficient IC ≥ 10 ; that' the definition for strong (...)

## Drawbacks of weak-inversion region?

How do you ensure that your operating point stays where you want it? That's the first trick. As VT slides around with temperature, are you then requiring that the circuit (centered at some subthreshold point) really work from cutoff to strong inversion when you throw PVT into the mix? Second is to be really sure that your subthreshold region is l

## inversion layer formation

Razavi book says: When inversion layer is being formed in a MOSFET, as the Vg becomes more positive, the holes will be repelled from the gate area leaving the negative ions behind and it forms a depletion region. When the negative ions are present in that region, why is it called depletion region ? If the negative ions are (...)

## Weak,strong inversion and velocity saturation region

What is the weak inversion,strong inversion regions and velocity saturation region? Especially, I wonder difference between strong inversion and velocity saturation region. Weak or strong inversion modes are operation modes of MOSFETs which differ in channel current (...)

## [Moved]: un*cox for nmos3v in TSMC

how to mesure un*cox for nmos3v in TSMC? You can calculate it from an Ids current measurement in strong inversion and linear region from this equation: I_{ds} = \frac {(\mu_n \cdot \, cox)}{2n} \cdot \, \frac {W}{L} \cdot \, (V_{gs}-V_{th})^2 For the substrate factor

## Channel formation in FD SOI

Electrons in the inversion layer are always provided by source or drain n+ heavily doped regions - irrespective of whether this is bulk device, fully- or partially-depleted SOI - assuming there is n+ region in proximity with the gate. (without n+ regions, electrons are provided through thermal generation in the depletion (...)

## Purpose of Double Guard Ring than Single Guard Ring

Concentric guardrings are common in ESD related circuitry (pad cells etc.). One useful function is that the built-in depletion region is a "getter" for loose minority carriers in the substrate. The ring can also kill lateral BJTs' base ohmically and deterministically if it is closed / pervasive, fight field oxide inversion / charging and so on.

## Short-length channel effects

I think this cannot simply be differentiated, because both effects (and hot-electron effects, additionally) depend on external conditions: Vds, operation region (strong, light or no saturation), and operation mode (strong, moderate or weak inversion) with different dependencies. I'd suggest to study these different ef

## Current peak at minimum transistor length

What do you mean with: " The transistor is powered in the threshold regime at 250mV".? The common terms to describe the operation region of a mosfet is either weak inversion (sometimes called sub-threshold) or strong inversion. The region between strong and weak inversion is called moderate (...)

## Is the device capacitance bias-dependent or independent?

Anything with a depletion region on either side of it will be voltage dependent. MOS channels swing from accumulation through depletion to inversion. Cgs follows gate voltage directly; Cgd, only when the channel is well lit near the drain (linear region - when it goes constant current the capacitance is sort of stood off from the (...)

## Flicker noise in FETs

Generally flicker noise tends to rise with Vov, see the following snippet. Hence triode region (large Vov, small Vds) will probably exhibit more flicker noise than saturation region. Still, operation in strong inversion mode (with large Vov and large Vds) would probably exhibit even more flicker noise in saturation region. (...)

## MOS substhreshold operation

Hello, As i read in the Gray Meyer's book, the drain current of MOSFET in weak inversion region is constant with different Vds. But when i simulated the operation of MOS in Cadence, the results show that the drain current is also change with Vds as in the strong inversion. Can anyone explain for me why? Does Cadence neglect the weak (...)

## sub threshold region

Subthreshold (or weak inversion) actually isn't a region of a MOSFET's output characteristic like off, linear = triode, saturation or breakdown region - which are identified by a Cadence ADE analysis, (together with No.3=subthreshold) - but much more an operation mode, classified by the deg

## why it is compulsary to provide an overlap between the source and drain with gate...?

The overlap between the gate and the source and drain region is required to ensure that the inversion layer forms a continuous conducting path between the source and drain region. Typically this overlap is made as small as possible in order to minimize its parasitic capacitance. Gate-to-Source/ Drain overlap assures good electro

## Current Steering DAC, Switch Transistors in Saturation or Triode??

Hello John, Score: --> 2 triode - 1 saturation (counting the senior guy) JGK Didn't you ask him for his reasoning? I increase your triode score: always used triode region in such case. Of course you can still reduce the mismatch if you use even larger FETs (= going to lower inversion coefficients) - b

## CMOS in weak inversion for generating PTAT

Regarding (4). I think that you need to have a sufficient margin from Vgs to Vth (my guess is 100m-150mV) otherwise they are going to move from weak inversion. If you use spectre you can see the region of operation. Check that the region=3 for weak inversion. Also the mos (not the one above the resistor) usually has higher (...)

## GBW and gm relationship of the subthreshold region Op-amp

Hello all Kindly, I eould like to ask how the transister working int the subthreshold region (weak inversion) has a high transconductance (gm) and hence high gain but small GBW. if we have high gm then we must have GBW as (GBW = gm/Cc). thank you

## PSPICE simulation parameters

can u please tell me the suitable parameters of the NMOS & PMOS devices for strong inversion region for ?5V power supply ??? I'll be thankful to you all... I am facing problem in my project... THANX ....PARASHURAM

## How to set the parameters for strong inversion region in PSPICE simulation?

How to set the parameters for strong inversion region in PSPICE simulation?

## Is this a good current bias

77088 vdsat is very large ,will this cause any problem? For what? For the VCO lock-in? Depends. M6 & M7 both work in strong inversion mode, so large vdsat is normal. M6 correctly works in saturation region, M7 in triode region however, which lowers the loop gain and inserts an additional(

## Region of operation of cascodes in a current mirror

To the simulator, as long as vdsat=Vgs-Vth<0, they will flag the MOS as operating in region 3, and defines it as the sub-threshold region. It's stupid. In reality, the region of vdsat<0 actually comprises of the week inversion region (sub-threshold), and part of the moderate inversion (...)

## Acceptable difference in range of Vds and Vsat to be in subthreshold region

I think your question isn't quite clear, may be you mix up subthreshold and saturation resp. linear region? Subthreshold (or moderate resp. weak inversion) is an operation mode, meaning in which range of Veff = VGS - Vth the FET is operated, whereas the linear or saturation region designate in which part of the ID vs. VDS characteristi

## how to find noise spectral density for the Bulk driven circuit

Please give some materials or method for finding noise spectral density for bulk driven MOS circuits operating in moderate inversion region???? Thanks in advance

## channel length modulation

I read that in an n-mosfet, when drain voltage is increased above threshold (in saturation mode) the inversion channel between the source and drain is pinched-off near the drain region. so the channel length decreases and so its resistance. so larger current flows through the channel. My doubt is, when a smaller portion is pinched off near the dr

## moderate inversion region

Moderate inversion operation usually is accepted for 0.1 < IC < 10 . IC = inversion Coefficient. For this region, Binkley states Veff=Vgs-Vth of -72mV < Veff < 225mV, s. this snippet from his

## what is "weak inversion region"?

weak inversion region and subthreshold region are the same regions. If you look at the cross section of the layout of a simple mosfet(nmos and pmos) you can see a virtual BJT b/w NMOS and PMOS thru which a current flows: leakage current. When your MOS is off(Vg

## Is there a lower bound on LDO dropout voltage?

To get a good regulation it is necessary to operate the pass transistor, too, in saturation region (in order to profit from its gm / gain). But even in weak inversion Vds,sat doesn't end up below 4Ut, see this image:

## weak inversion current

In weak inversion the current varies exponentially with gate-to-source bias VGS as given approximately by 58417. where ID0 = drain current at VGS = Vth, the thermal voltage VT = kT / q and the slope factor n is given by n = 1 + CD / Cox, with CD = capacitance of the depletion layer and COX = capacitance of the oxide layer.

## MOSCAP (MOS Capacitor)

hi What is MOSCAP? Please explain me accumulation depletion and inversion mode. Any practical use of MOSCAP?

## Weak inversion region design

Hi, I want to design an OTA in subthreshod region. But i don,t know how must start my design. OTA have 1v Vdd. gain=52db and I(vdd)<100nA Please help me as soon as possible. Thanks

## How to choose W/L ratio for MOSET working in the W.I region?

Hi guys, My method is : 1.let gm of weak inversion equal to that of strong inversion which is: gm=ID/(nUT)=2*ID/Vdsat; 2.therefore, we have: Vdsat=2nUT; 3.ID=0.5*K*(W/L)*(2nUT)^2 For example, if we want 100nA current flow through MOSFET which is working in the W.I region, (since n=1.2~1.5, let n=1.2), we have: (...)

## gds of a MOSFET in the weak inversion region

I have been working with MOSFETs in the weak inversion region and I am noticing some problems with the value of gds (conductance between source and drain) in both my hand calculations and PSPICE simulations. When simulating in PSPICE the output file tells me that gds = 3.70E-08, however when I use Id/Vds=gds I get 1.05E-6. Do MOSFETs in the weak

## Two gm/Id questions - need explanation

I also have question similar to 1. Essentially, some of the the papers on gm/id methodology use the strong inversion and weak inversion regions ? e.g the output stage in a different region, why should that be ? Any explanation would be appreciated!

## [Help]CMOS comparator design questions.

Hello All, I have some questions about cmos comparator design. I need to design a very low power comparator. The Vdd = 3.3V, Midband Gain ~55dB, GBW ~500KHz. The current needs to be as small as possible. I plan to put the differential pair in subthreshold region and the rest of the transistors in strong inversion or moderate (...)

## calculation w/ EKV + simulation w/ BSIM = confused

Hi, It seems there is more talk about EKV and gm/id on this board recently so maybe someone can provide me with some help... I have done my hand calculation using EKV model but my PDK uses BSIM model. How can I ensure that my hand calculation is correct regarding inversion coefficient (IC)? Should I consider the BSIM region parameter as havin

## Weak inversion biasing - need for or advantage of

What is the (need for/advantage of) biasing a transistor in Weak inversion region? Plz list some tutorials if anyone might know! Sidharth

## Lowest possible Vdsat. Could it negative?

As Vgs-Vt approaches zero, the device is no longer working in strong inversion, and a different set of rules occurs because the conduction is no longer dominated by drift. Using vdsat = vgs-vt is only valid in the strong inversion region. The device goes thru a transition region (moderate inversion) (...)

## Ask help of the debugging of an OTA

Hi guys, I just pick a particular configuration of the OTA using cross couping technology(the circuit and the CMFB are in the attachment 1 and 2). But what I get in testing the Gm is not flat,(the third attchment ). The MN3,MN4 are in the weak inversion and MN1,MN2 are in the triode region .I don't know why I cannot get a flat waveform in the part

## LNA IIP3 vs Input RF Power Plot

This phenomenom is called "Sweet Spot" where the transistor is in the region between weak inversion and saturation, so the third and fifth derivatives of gm is going to 0 so the IIP3 is improved.

## the input pair of opamp operates in weak inversion?

if i have an opamp, the input pair or some of load transistors operates in weak inversion, what results will cause?

## Biasing Transistor in Weak Inversion

Under inversion from Willy sansen's notes, you will have three inversion region: weak inversion, strong inversion and velocity saturation region and those depends on how hard you bias the Vgs. IDS in strong inversion resembles (Vgs-Vt)^2 law, while weak (...)

## design folded cascode op amp using gm/id method

Hi all, Currently i m designing folded cascode amp by using gm/id method. My problem is that, i don't see how are we going to bias drain voltage by using this method. This method only describe the gate biasing (inversion region) and W/L ratio. Also, the paper mentioned that only EKV model has modelled the gm/id behaviour properly. Does it mea

## cmos current generator

Hi, I'm trying to construct a Iptat2 current generator, which is on the scheme. I've got a problem with getting my transistors T1 and T2 in the subtreshold region. They should work in subtreshold region, while T4 should be in strong inversion and this equation should be true: Iout=((2*(Beta4^2)*(Vt^2)*(ln(Beta1/Beta2))^2)/Beta3, where Vt (...)

## very low operational transconductance amplifier (OTA)

10nA/V looks like impossible low. Check your specification. inversion coefficient == 10 means strong inversion, when overdrive voltage Vov~0.2V (u use Veff term). Keep in mind that when Vov~0.5V and goes higher it's possible velocity saturation effect. In this region transconductance becomes independent of current exept W/L ratio. Try to (...)

## Why MOSFET IS OPERATED in Saturation region.................

At the low-current end(weak inversion), we do not want to use the weak-inversion current region either. The absolute values of the currents and of the transconductances become so small that the noise becomes exceedingly large. Moreover, only low speeds can be obtained. At velocity saturation region: gm(sat) does not (...)

## Getting good matching offset in folded cascode OpAmp

See my post and reference links on: The best case for matching is diff. pair and cascode MOSTs working in weak inversion region and mirror MOSTs working in strong inversion region. Be care with rail-to-rail input because offset voltage will change with input common mode voltage.

## How can to reduce offset in input terminal of OPamp ?

Layout and Circuit. Use input diff. pair with large area MOSTs operating in weak or moderate inversion region. Use well matched load of diff. pair, proper sizing and strong inversion for current mirror. One of source of systematic offset is difference of drain-source voltages of input diff. pair. U can eliminate this with proper biasing (...)

## Sub-threshold saturation--is that ok?

Sub-threshold (aka weak inversion) region is normal for diff. pair of OPAMP. In this region u've maximized transconductance efffectiveness Gm/Id. This gives u an advance in terms: gain (Gm*Ro=>(Gm/Id)*Va), GBW (Gm/Cc), Input Refered Noise, Input Offset/Matching (offset close to threshold voltage mismatch). At the another side the slewrate (...)

## Rds of the MOS component

Usaully Rds mean mos resistence when it is in triode region?Why would you want to know Rds of mos in weak inversion(subthreshold)?