M80/7, Electronics Research Laboratory University of California, Berkeley, October 1980)ģ MOS3, a semi-empirical model(see reference for level 2)Ĥ BSIM (see B. Liu, The Simulation of MOS Integrated Circuits Using SPICE2, ERL Memo No. The model parameter LEVEL specifies the model to be used. There are seven monolithic MOSFET device models. LTspice contains seven different types of monolithic MOSFET's and one type of vertical double diffused Power MOSFET. The temperature specification is ONLY valid for level 1, 2, 3, and 6 MOSFETs, not for level 4, 5 or 8 BSIM devices. The optional TEMP value is the temperature at which this device is to operate, and overrides the temperature specification on the. TRAN control line, when a transient analysis is desired starting from other than the quiescent operating point. The initial condition specification using IC=VDS, VGS, VBS is for use with the UIC option on the. OFF indicates an initial condition on the device for DC analysis. PD and PS default to zero while NRD and NRS to one. NRD and NRS designate the equivalent number of squares of the drain and source diffusions these values multiply the sheet resistance RSH specified on the. PD and PS are the perimeters of the drain and source junctions, in meters. If any of L, W, AD, or AS are not specified, default values are used. Note that the suffix u specifies µm and p square µm. AD and AS are the areas of the drain and source diffusions, in square meters. L and W are the channel length and width, in meters. Nd, Ng, NS, and Nb are the drain, gate, source, and bulk i.e., substrate nodes. Monolithic MOSFETS are four terminal devices. The model card keyword VDMOS specifies a vertical double diffused power MOSFET. The model card keywords NMOS and PMOS specify a monolithic N- or P- channel MOSFET transistor. The MOSFET's model card specifies which type is intended. If you want a gate with a more powerful output, capable of driving many inputs, you would keep L at the minimum but increase W.Symbol Names: NMOS, NMOS3, PMOS, PMOS3There are two fundamentally different types of MOSFETS in LTspice, monolithic MOSFETs and a new vertical double diffused power MOSFET model. But that increases the size of the transistors! You could also make a much slower/low power version by increasing the value of L. Usually 2x wider is a good start so 400 nm for example.
As PMOS transistors are intrinsically weaker they need a wider Width compared to the NMOS. The Width for the NMOS is set to a workable minimum like 200 nm, that depends on the process. Selecting the W/L ratios of the transistors in these cells is usually trivial, Length is set to the minimum so 32 or 45 nm. So if you designed a digital circuit consisting of gates then you can use ready-made cells for that so you do not have to worry about W/L. These gates are mostly pre-defined with transistors having a certain W/L and a layout of these transistors and their connections.
Nmos transistor typical length code#
Fortunately almost every schematic drawing program offers an option to generate a netlist.įor digital circuits the netlist is usually generated from the RTL code which describes what the circuit looks like in terms of gates. As a designer of a digital circuit you generally do not have to worry about the W/L ratio of the transistors.Īctually a schematic and a netlist describe the same thing! They both describe how all components are connected to eachother.Ī schematic is easier to read for humans, a netlist is what a computer program expects as input.
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