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66 Threads found on Mos Width Length
Hi, By boss tells me that to get good matching in current mirrors they should be designed where L is large. My own understanding that as long as the devices are large in area and laid out well then they will match. So my question is length important or is making the area of the mosfet large sufficient? Thanks
Hi again, I have not got any replies. Obviously somehow the quote symbol did not show up correctly. The correct sentence follows: For example now as width/length values I have (5u/1u), but what I want is: (W=5u/L=1u). I also have encountered another problem. I have added another attribute: (nfing) for the number of fingers per mos (...)
when you design power mos, you design for output resistance usually. for example, a 2 ohm nmos can sink 5A from a 10v rail, but only 0.5A from a 1v rail. highest layout density is from the waffle layout, but it suffers from early wearout and low esd. (ie-all the right angles cause field concentration and hot carrier/esd weakness) so my sugg
Hi there, Currently, I am a student and working OTA with switch-capacitor CMFB and later going to switch-capacitor amplifier design. I am wondering which is the best mos switch aspect ratio. Say, for TSMC 0.35um technology with 5v process, the minimum length is 0.5 micron. So how can I choose the W/L for Nmos switches in (...)
Do you mean the parameters given in a SPICE file? If yes then which level. The higher level models do not have λ as a parameter. Its always better to derive these parameters by plotting the DC curves of a mos device of known length and width for your hand calculations.
I am using model of CSMC.The gate-width of nmos and pmos are not found in the netlist, but gate-length exist. I see the CDF of nmos and pmos, the parameters of gate-width are the same as gate-length.I can't find the reason. Thanks!
Hi, friends: We can export the CDL netlist from Cadance, like: M*** d g s b PV W=10u L=2u M=1 R*** net1 net2 NumberOfsheet $ But CDL netlist can't be simulated directly using Hspice, we must find and replace. Does there exit method to export the Hspice netlist that can be recognzied directly by Hspice simulator with
We ofen mixed 2 mos (Current Mirror ) by finger. We get the same Rs of mos , and can improve matching .
1. after netlisting, if the NRD does not exist, does that mean NRD=0 2. how to calculate NRD length of drain/width of drain or 0.5 length of drain/width of drain(since the contact is in the middle) Thanks
Hi, For the Transmission gates we use the minumum width of Nmos and Pmos. I have no idea for the flip-flops.
how to add the mos As,Ad,Ps,Pd (area of source & diff, perimeter of ....) in cadence? i.e. what are their equations? and can i enter them as equations? or i have to change them every time i change a mos dimensions.
Basically the wider the width of mos more current will pass through mos on the other hand there is an increase in parasatic capacitance. If you say if an Nmos with width x take t psec to discharge a load capacitance then a Nmos with width xx>x will take tt
echo47 Thank you for your reply . Yes it is 12.5MHz for the peroid 80ns, it is my error. Sorry I could not provide a schematic for you. In my project, I want to use a mos campacitor connecting one input node of the comparator to attenuate the noise from the other input node. So I prefer to minimize the mos width and (...)
i cant post the link but , if you search for ECE-E432 Microelectronics II Drexel University Electrical & Computer Engineering Lab 1. - mos Device Characterization that lab should be helpful
Hi __| __|| | ||__ __| | | __| |__|| ||__ | this will act as a W/2L mos transistor (in sat region). regards
This lambda and the lambda in mos current equatuins are same or different? They are two different. lambda in layout is Lmin = 2* lambda lambda in mos current equation is Channel length modulation factor This lambda is related to 1/VA Where VA is Early voltage tnx
Look into a design manual. They usually extract models for specific W and L of mos device. Those are the "exact" values. Then they include scaling which is theoretical approximation. I use max W as 10um and if I need bigger size I use parallel multiple. Then you can use virutaly any W you want. L is the litography limit for the technology. For d
Hi, all If I make a mos transistor's width longer than its length in an IC circuit, is there any drawback by this way, especially in the layout level?
In what way mos overtaken BJT ?? plzz explain briefly One thing, that it's easier in integration and fabrication as its geometry is much simpler than BJT, and with nowadays short device lengthes, it can acheive high speed as BJT in the past.
Hi, can anyone tell me what the minimun channel length for a mos transistor for AMS 0.35um process, and why follow the LAMBDA rule for width and length for cmos transistor.
We often use this type mos as large resistor. I wonder if there are some rules in thumb for using this "inverse W/L ratio" transistor.
how to determine channel length, L and channel width, W of mos transistor? i want to simulate a Cmos comparator but i dont know how to determine W and L?
The more detailed you make the simulation (you should simulate this) the more accurate your resistance calculation. Metal 1 resistance usually overwhelms all the other metal resistances because it is in narrow stripes on the drains and sources. One half of the mosFET has all the metal 1 strapped with vias to metal 2, the other half is a long metal
Hi, For simple rectangular mos transistors, it's easy to identify width and length depending on direction of current flow. If you've complex irregular mos transistor (not like a spider :D but mostly like a rectangle having many glitches from one or both sides), is there a scientific method in this case (...)
is there any problem if we do not keep the drain and source areas same width and length like emitter and collector in bipolar junction transistor???????? thanks..
Hi all, I have kept Nmos width constant and sweeping Pmos width. Results show that fall time is increasing drastically. What are the reasons for the increase of FALL TIME?
In a typical inverter, Nmos pulls the output to low, while Pmos pulls the output to high. To increase the threshold, you need to increase the strength of the Nmos and/or reduce the strength of Pmos. The strengh of a mosFET is decided by its W/L (width/length) ratio. The (...)
Can any one tell, whether the line width and the channel length are same! what is meant by line width of a mosfet? and please provide me some examples!
Where to define the V-I characteristics of a new created device\part. e.g., I have to use mos and I created my own part using ?NEW PART? in ?USER DEFINED PROPERTIES? i added new property width, length but where I have to give the characteristic equation which defines the relation of voltage, current, W/L ratio and other parameters.
for nmos transistor the on resistance Ron is given by the equation Rtransistor =Lg0/(width* mu *COX*(VDD-VT0)) i use the following values Lg0 17.5 nm -> .0175 micro meter width 140 micro meter this make w/l =8000 which i think very reasonable VDD 1 volt VT0 0.18 volt from my model i found COX 3.137727e-14 farad per Micro (...)
Hello the minimum length cannot be used in the analog design circuits, usually you need minimum of 2*min L and that because of : 1. minimum length has worst case matching 2. has higher channel length modulation that we never like since it will degrade the mos transistor output impedance and hence degrade the design of the (...)
Hi, So I need to make sure a mos Cascode along with other devices in one (vertical) arm of the circuit lying between VDD and GND doesn't collapse under all corners. For this i usually make sure the VDS (or the VCE in Biploar) doesnt go below say 250mV (or about 300mV in Biploar) in a nominal run, say a dc sweep over temperature. I see ther
Hi, 1. Which skill function can change a mos' length and width in the schematic? 2. Whcich skill function can be used to flatten all layout database ? 3. Which skill function has sizing function for layout database? 4. Is there a tool can follow the design rule to automatic sizing layout database? Thanks.
1. measure the open loop gain. the most important parameter is the input offset voltage. check on these a rule of thumb, the length of the mos is 2-5 times bigger than the min length. for the width, consider the matching and the current mirror.
Based on mos working situation, doing device simulation to get the suitable lenth maybe a effective method.
Hi, I use BSIM3v3.3 mos transistor models for RFIC design. BSIM 3v3.3 does not include a substrate network but just a drain-bulk capacitance which may be insufficient at high frequencies. I decided to use a grounded substrate contact surrounding the transistors to reduce the substrate resistance. The distance between the transistor and the cont
Why does the threshold voltage of a mos increase when we increase the L of the transistor?
If we have 2 mos with exactly the same VDS and VGS, the same lengths, but widths in the ratio say 25:1. Why shouldn't the currents be in the ratio 25:1? I am asking this because simulations don't show the current ratio to be 25:1.
yes if you want to design IO by yourself , first you shold konw some analog knowledge, layout design method is also needed, ESD and ESD protect circuit and Latch are necessory, if the foundry are detemined, normally foundry will recommend you the ESD protect circuit structure and detail design parameter, such as, mos length,width, resistor, (...)
If you've done IC layout, be it Analog or Digital/ASIC, you will wonder how to calculate the cell area. Well, here are some rules from which you can calculate the area... 1. Resistor Area: Ar = 1.2RWr(Wr + Sr) / Rs Where: R = Desired Resistance Rs = Sheet Resistance Wr = width of the Resistor Sr = Spacing between
Usually mos transistors in triode region are used for switches. Depending on the configuration, either an Nmos or a Pmos or a combination of both is used. The length of the mos is kept minimum to reduce parasitic capacitances. Depending on the application, the width is adjusted. (...)
hi, If you want to analyse the mismatch of Band gap, the mismatch parameters from the foundry are needed. For example, the 3.3V Pmos Vtsat mismatch parameter is 4.9mV*um. If you want to know the Vt mismatch of a Pmos current mirror with size of W=10um, L=5um, the Vt mismatch equals to 4.90mV*um/sqrt(10um*5um)=0.693uV. Normally the (...)
it means that channel lenght is short :D, u know the mos is isolated gate device, where the gate potential "metal, infact polysilicon" is used to control the flow of the current in the mos , the metal gate dimension are length "L" and width "W" , the current is proportional to the aspect ration W/L"this means that aboslute (...)
Hi, that was my question.. How is area occupied by the mos calculated given the spice model regards
just be curious how to choose the w and l of a mos fet example,in the pic,a larger l and smaller w campared to lower one is chosen to produce a lower common mode output voltage(hen
Hi all, I have read a paper mos Operational Amplifier Design? A Tutorial Overview by P. R. Gray recently, but there is something I can't understand very clearly. So I think I need your help. Here it is: For constant drain current decreasing either the channel length or width results in a decrease in the gain, the latter because of the fact (...)
Hi, I also had the same situation like you.But My circuit at mos level,so I checked the Lenght of transistor,and I found it not valid with Model. I think you should check your circuit again(it maybe run in Winspice but not in T-spice)
The bias will change when VDD, corner, temperature and resistor variation. I don,t know your application, So I cann't comment more about design.Maybe you don't care the bias variation, and the slew rate symmetry. "but different width is okay to apply in the layout design? " You can let the width of large mos and small (...)
How does dracual LVS extract channel width and length of mos in layout? and, if i want to change the formula for calculating the value of W or L, what should i do? It is always easy for calibre lvs users to find the expression and revise. Thanks in advance
Hi,all How does dracual LVS extract channel width and length of mos in layout? I mean how the "W=** L=**" expression is obtained by dracula lvs run. This expression is locating on the right side(layout devices, nodes and parameters) of .lvs file? and, if i want to change the formula for calculating the value of W or L, even those of (...)