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75 Threads found on edaboard.com: 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 (...)
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? I have also read some paper and some write, when Vgs-Vth0>100mv it is in strong inverison region. Please help.
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
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 (...)
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 (...)
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
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 (...)
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.
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
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 (...)
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 (...)
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. (...)
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 (...)
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
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
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
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 (...)
how the transister working int the subthreshold region (weak inversion) has a high transconductance (gm) and hence high gain but small GBW. Transistor working in the subthreshold region (weak inversion) has a low transconductance (gm)! gm/Id is high.
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?
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(
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 (...)
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
Please give some materials or method for finding noise spectral density for bulk driven MOS circuits operating in moderate inversion region???? Thanks in advance
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 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
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
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:
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.
hi What is MOSCAP? Please explain me accumulation depletion and inversion mode. Any practical use of MOSCAP?
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
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: (...)
First, you don't mention what your technology is. Generally, in weak inversion currents are small and hence you can expect higher values for ro, respectively lower values for gds. The formula that you gave gds=Id/Vds is not correct if Id and Vds are your dc values. The question you asked: "Do MOSFETs in the weak inversion region act (...)
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!
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 (...)
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
What is the (need for/advantage of) biasing a transistor in Weak inversion region? Plz list some tutorials if anyone might know! Sidharth
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) (...)
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
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.
if i have an opamp, the input pair or some of load transistors operates in weak inversion, what results will cause?
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 (...)
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
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 (...)
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 (...)
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 (...)
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.
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 (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 (...)
Usaully Rds mean mos resistence when it is in triode region?Why would you want to know Rds of mos in weak inversion(subthreshold)?