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Check the manual, for the current there are special symols for Ids/Igs etc. So you need to save them and then plot
hi, I am using TSMC0.18 in cadence mixed signal design domain for designing of opamp. I am able to plot gm/Id versus Vgs and Id/W versus Vgs curve. but I wanna plot gm/Id versus Id/W in Cadence. What is the exact circuit to plot this ?
How to find the I-V characteristics Id versus vds? of an NMOS transistor Also.. How do I sweep the VGS and vds from 0 to 3V? I am having a bit of trouble using spice, if anyone knows a good tutorial "for dummies site" please let me know...
hey,moonnightingale here's my answer , I hope it can be helpful. As the nmos is in the "Saturation Region" and the current source is a dc source, it means: Id=0.5 * Un * Cox * (w/L) * (Vgs-Vth)^2 * (1+λvds) and here ,Vgs=vds : Id=0.5 * Un * Cox * (w/L) * (vds-Vth)^2 * (1+λvds) the right part of the equation (...)
plot id vs. vgs in cadence then take the derivative of the curve
hello Is every spice model suitable to plot gm/id curve? how should the analysis look like. i use .dc ibias start stop step but i think it's not correct any examples? regards
there is not a sharp transistion from sub-threshold operation to moderate inversion. Usually, when you have the Id ~ Vg curve with the fixed vds, you will get a somehow constant slop curver after some Vg, just extend that curve toward you x-axis and the intercept point will be quite accute of your Vth
i hav to design a fully diff amp...using gm/Id method to meet the specifications... generated gm/Id curves for nmos(SOURCE connected to GND,DRAIN and GATE shorted and swept the DC voltage from 0 to 3.3v).....but facing problem how to generate the gm/Id curves for the pmos using spice cud anyone plzz tell the connections n how to pe
Thanks for holddreams's reply. If vth is not equal to vth0, how should I set Vgs in spectre? is there any ideas?
Phenomena like DIBL will lower the effective VT of FETs in absolute terms. None of the lengths you show are likely to see much of this in submicron technologies. Edge effects may also be a factor, a small region at the edge is a somewhat effective MOS structure but with some degraded attributes from strain and oxide / interface quality.
hi all, when i plot the Id Vs vds for different Vgs , the current is increasing with the increasing Vgs which is normal. but my question is why the slope is also increasing with increase in Vgs. mathematical explaination would be helpful. please help me. Thank you.74989
Yes. The transistor enters saturation only at red line points but the region between green and red lines is also considered as Active region or Triode Region of the transistor's operation. All the best. I agree with sunny too. - - - Updated - - - Yes. Its no load condition only. U got to see its model properties for furt
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
The datasheet should show Id leakage current versus vds.
Depends on what you need in your application: you may choose between constant Id constant vds Vdg = 0 ("diode connection") See this example 107438 and tutorial: 107439
it works like this..... 1) We first set the vds and ID or VCE and IC at a fixed value to ensure that our devices(mos or bjt) will first of all act as a linear VCVS or CCCS respectively....hope u understand this first point correctly. 2) Next once the "Q" points have been set correctly, now we "send in" or "inject" a very "small signal".....I
please understand that in submicron processes mosfets...I mean if your mosfet's length is less than 1um then the whole device model equations break down ...WHATEVER IS GIVEN IN GRAY AND MEYER DOES NOT WORK ANYMORE ACCURATELY ENOUGH for the submic mosfet!!! furthermore please understand that if your mosfet model is BSIM3 based...which I am quite
Clarify how high output impedance is achieved with minimal length .Higher L would give higher output impedance . Coming back to the query ,People use channel lengths typically 4 times the minimal channel length ,there is not rule of thumb but one could measure the slope of Id vs vds curve in saturation region ,look at the slope and decide on the
its written 50 ohms but it may not be 50 ohms. devonsc you are right about the voltage required to turn on the MOSFET. the datasheet says that the threshold gate-source voltage Vgs(th) is 1V so anything above that will surely turn on the MOSFET. the vds is the drain to source voltage which depends on the drain to source resistance when the MO
thanks, my default annotation results in transient op include ids,vgs,vds, i wanna add vdsat to be annotated, how can i do? thx
plot Id vs vds for different Vgs and measure the slope of the curve in sat region and use lambda =(Id2-Id1)/(vds2-vds1) hope this works
Dear all, When I calculate K'n=(0.5)?nCox, I have a problem. By TSMC 0.35?m SPICE model, I know these parameters (TT case): (1) U0=0.04660162 (NMOS) (2) tox=toxn=7.5e-9 (3) λ=DELTA= 0.01 (4)Vth0=0.536027 And, we know that ε=εox*ε0=3.9*8.854e-14F/cm=3.46e-11F/m also know that Cox= ε/tox so, w
Hello, you can think of it in two ways: 1. As voltage, forget about the currents now, and check the path of small signal from CM sense and back to it, check wether the increase at some point will lead to increase or decrease on another "for common source it's inverting , for common gate it's non and so on." 2. As current, remember that as
*The following is the nmos.sp files simulated by Hspice. *Size nmos device by plotting Id versus V*=2*Id/gm mn dn dn 0 0 n33 w=10u l=1u m=1 vdn dn 0 dc 1v .dc vdn 10mv 3.3v 10mv *Note that vs is v*.. .probe vs=par(`2*i(mn)/gmo(mn)`) .probe Id=par(`i(mn)`) .option post probe list node dccap brief ingold=2 measdgt=6 numdgt=8 .lib `./m
Dear all, I want to plot the NMOS transistor drain current mismatch σ(ΔID/ID) versus effective gate voltage VG − VT curve by using hspice. How should I do? Example as shown below.
hi you are mistake M16 is current mirror so we have current of M16 so we have |Vgs9| and so we have PCS3 and vice versa if we have PCS3 we have ID9 and Vgs16. regards
Hi, You would have to calculate the value of CLM from plots. Get the Id Vs vds transfer characteristic for the MOS. Use the claculator function in ADE and chop the curve so that you have curve for saturation region. Extrapolate the lines to X axis and get the early volatge value. Inverse of that would give you CLM value. You can you equatio
the main idea is that in the case of small signal behaviour the part of the transfer function we would be working on can be assumed linear which is not the case for large signal.... so the variation of parameters of MOS transistor with voltage and current levels need not be considered for small signal...
Hello, all The attached file shows the relationship between Id and vds under the same Vgs and size.The black curve is the normal curve and i want to get the red one, which behaves differently from the black one in the weak and moderate inverision, by changing parameters in the spice model.I was wondering how to get the red curve by changing para
does anyone know a single test bench that will allow me to calculate gm*rds for an nmos? ie be able to simultaneously get IdVsVgs and Id Vs vds curves
$ Problem 1: Size pmos device by plotting Id versus V* = 2*Id/gm mn dn dn 0 0 pmos L=1um W=10um vdn 0 dn dc 1V .dc vdn 10mV 3V 10mV * Note that vs is V*... .probe vs = par('-2*i(mn)/gmo(mn)') .probe Id = par('-i(mn)') .options dccap post=2 brief .lib 'cmos35.txt' nominal .end how to plot this waveform using scope?
Hi, According to datasheet the Vgs(th) is less than 0V which is GND potential. According to charctaristic curve for 'Id' vs 'vds' at given Vgs, the curve shows that more current paas through if Vgs is less than 0V and for 0V Vgs there is no curev which shows no corrent or may be I am not understanding the datasheet but it looks like the MOSFET nee
vdsat = Vgs - Vth What you name "vdsat" just marks the transition voltage between the linear (or triode) and the saturation region (or the transition from weak to moderate/strong inversion) for any drain current Id, see the dotted curve in this Id vs. vds plot from
mani1, You seem to be looking for transistor level information. Just in case you are also interested in saturation mode operation you should check out . It has many interactive digital circuits, articles and videos. It may have answers to many of your questions. Also it has an online simulator:
Hello all, In my first assignment to Analog course, I have to plot second and third order derivitive of IV curve of NMOS transistor. I was able to do the first order rds = 1/(δId/δvds) using calculator (1/deriv(IDC("NMOS/D"))) but I'm not sure how to get the second/third order. Any input would be appreciated, Thanks!
Hi, I was wondering what would you do after get the spice tech library. I'm a little bit confused about what parameter and plot should I get. I think at least gm, ro, lamda...and etc should be known, the question is how to get them? Here's a list that I can think of: id vs vds plot, sweeping vgs gm vs vds plot gm/id plot if necessary r
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 different
Dear all members and analog IC designers.. I am student attending final course, now I am using Cadence IC and want to simulate to design rail-to-rail OpAmp using design kit gpdk045 (45nm) .I want to simulate the OpAmp from the following articles.First of all I want to simulate the input stage target design is as follow: Open Loop Gain
Hi, While annotating the transistor for its operating point, i can display only 3 types of component display properties (eg, Id, Vgs, vds or any other 3 types)... but if i want to display more than 3, say 4 or 5 such type of properties .... is there any way? thanks
Hi, While annotating the transistor for its operating point, i can display only 3 types of component display properties (eg, Id, Vgs, vds or any other 3 types)... but if i want to display more than 3, say 4 or 5 such type of properties .... is there any way? thanks
You can extract parameter lamda by using simple simulation of Id Vgs vds and also you can use the analysis and statistic method, refer to Allen book Appendix B. Good luck!
Hi I used the following equation in order to model the MOS current in subthreshold region: ids=I0* exp((Vgs-VT)/(n*Vth))*(1-exp(-vds/Vth)) ? With Vgs=100mV, I ploted the current versus vds. But the result is diffferent from the
hi all, im doing project on dual material gate silicon on insulator using athena and atlas.does anyone know how to create code for dual material gate?do the gate have to be differ in terms of concentration or what? i have tried but for id versus vg curve,there is some voltage drop at certain value.i dont know which part need to be adjust. an
you are partially right. the MOS current is: Id=unCox/2*W/L*(VGS-VTH)^2*(1+lambda*vds) so, if u differentiate Id with respect to vds, you obtain lambda*Id. the derivative of Id(vds) to vds is the slope of Id(vds). You divide it by Id and you have lambda for a given bias point.
for ideal circuit, why the graph of I versus vds are same for equal transistor sizing but not equal in w and l. let w=10um,l=5um and w=5um, l=2.5um, why their characteristic are same???
With C@dence' ADE calculator (use the derivative function) identify gds at your selected bias point, then calculate the Early voltage If you don't like to calculate, I think it should be possible to determine the slope a of the curve via the simulator as a number. Then, you can command to
Hi, How can we define quantitatively the variation of Id and Gm versus the input voltage for a common source with source degeneration resistance. My assumptions are as follows: Variation of Gm versus Vin Until Vth since there is no channel and hence current flow, the Gm should be Zero Above Vt
Then how does this affect MOSFET behavior? It affects the carrier speed and thus the behavior of the Id vs. vds characteristic. For more info I'd suggest to read textbooks about Analog Circuit Design.
You can plot Id vs. vds and extrapolate to the crossing point with the horizontal axis. But this is a lost battle - for sub-100nm technologies, ro varies all-over the place. You'll most probably get different lambda values for different Vgs. Not to mention that if well modeled, the ro will vary also with the vds.
Channel length modulation (CLM) strongly depends on channel length itself, on vds and on inversion operation mode, hence should be extracted at an appropriate operation point. On absence of other conflicting effects which may also affect the gradient of the Id-vs-vds characteristic (DIBL, hot electron injection), the CLM parameter λ can be