{"id":2056,"date":"2018-05-07T08:57:03","date_gmt":"2018-05-07T08:57:03","guid":{"rendered":"https:\/\/www.tina.com\/resources\/?page_id=2056"},"modified":"2018-06-22T09:10:02","modified_gmt":"2018-06-22T09:10:02","slug":"7-fet-models-for-computer-simulations","status":"publish","type":"page","link":"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/7-fet-models-for-computer-simulations\/","title":{"rendered":"7. FET Models for Computer Simulations"},"content":{"rendered":"<div class=\"top-navigation\">\n<div class=\"current-page\"><img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/people-location-30.png\" \/>CURRENT &#8211; 7. FET Models for Computer Simulations<\/div>\n<div class=\"previous-page\"><a href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/6-comparison-of-mosfet-to-jfet\/\"><img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/leftarrow5.png\" \/>PREVIOUS- 6. Comparison of MOSFET to JFET<\/a><\/div>\n<div class=\"next-page\"><a style=\"font-size: 20px;\" href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/8-fet-amplifiers-canonical-configurations\/\">NEXT- 8. FET Amplifiers &#8211; Canonical configurations<img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/rightarrow5.png\" \/><\/a><\/div>\n<div class=\"clear\"><\/div>\n<\/div>\n<p><script>\nfunction setStyle(){ \nheight = document.getElementsByClassName('entry-header')[0].clientHeight;\ndocument.getElementsByClassName('entry-header')[0].style.marginTop = height +\"px\";\ndocument.getElementsByClassName('top-navigation')[0].style.top = Math.round(-(height-20)*2) +\"px\";\n}\nsetStyle();\nwindow.onresize = function(event) {\nsetStyle();\n};\n<\/script><\/p>\n<p align=\"justify\"><strong><em><span style=\"font-size: 22px;\">FET Models for Computer Simulations<\/span><\/em><\/strong><\/p>\n<p>SPICE and MICRO-CAP contain sophisticated models for JFETs and MOSFETs. The JFET model (the SPICE 2G.6 model) contains 12 parameters. The MOSFET SPICE model contains 42 parameters in three levels. The lowest level model contains 25 parameters, while higher-order models add to this list. MICRO-CAP additional 10 parameters to the MOSFET model to bring the total to 52. The more parameters the model uses, the closer the simulation results are to the actual device operation. However, the more parameters in the model, the slower the simulation runs.<\/p>\n<p>The reason there are so many parameters is that the model attempts to closely imitate the nonlinear operating curves of the device. The computer is capable of tracking far more details than we can by hand, so the model can be more sophisticated than that we use for a &#8220;paper&#8221; solution. In many analysis situations, you would set most of the model parameters to their default values and this complex model behaves almost the same as the simplified models we have discussed. While we discuss SPICE in an Appendix of this text, we will now quickly review the syntax for including a JFET or MOSFET in a circuit. The SPICE statement for a JFET is of the form,<\/p>\n<h6><strong>Jname nd ng ns modelname [area] [OFF] [IC=vds[,vgs]]<\/strong><\/h6>\n<p>Square brackets indicate that the quantity is optional. As an example, you might include statements,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2088 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-SquarebracketsV.png\" alt=\"\" width=\"555\" height=\"73\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-SquarebracketsV.png 555w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-SquarebracketsV-300x39.png 300w\" sizes=\"auto, (max-width: 555px) 100vw, 555px\" \/><\/p>\n<p>The 10, 11 and 12 in the first statement are the node numbers for the drain, gate, and source. U308 is the model name. The area, which defaults to unity, multiplies or divides parameters for the model. The &#8220;OFF&#8221; instruction turns the JFET off for the first operating point. The &#8220;IC&#8221; sets initial conditions for the drain-to-source and gate-to-source voltages. The initial conditions are only used for transient analysis. The second statement is used to define the device having name U308 as an <em>n<\/em>-channel JFET with <em>V<sub>p<\/sub><\/em> (VTO) set to \u20134V and <em>K<\/em>(BETA) equal to <em>K<\/em> = <em>I<sub>DSS<\/sub>\/V<sub>P<\/sub><\/em><sup>2<\/sup>. For a\u00a0<em>p<\/em>-channel JFET use the designator PJF instead of NJF and set the parameters VTO and BETA to match the <em>p<\/em>-channel parameters.<\/p>\n<p>The following table lists the 12 parameters in the computer simulation model. It also shows the default value and units for each parameter.<\/p>\n<div id=\"attachment_2066\" style=\"width: 604px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2066\" class=\"wp-image-2066 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-2.png\" alt=\"SPICE JFET Parameters\" width=\"594\" height=\"308\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-2.png 594w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-2-300x156.png 300w\" sizes=\"auto, (max-width: 594px) 100vw, 594px\" \/><p id=\"caption-attachment-2066\" class=\"wp-caption-text\">Table 2 &#8211; SPICE JFET Parameters<\/p><\/div>\n<p>The model associated with these parameters is shown in Figure 29.<\/p>\n<p>The SPICE MOSFET model is considerably more complex than that of the JFET. The lowest level (<em>level 1<\/em>) model contains 25 parameters which are detailed in Table 3. The SPICE statement is of the form:<\/p>\n<h6><strong>Mname nd ng ns nb modelname<\/strong><\/h6>\n<p><strong>+[L=length][W=width][AD=drainarea][AS=sourcearea]<\/strong><\/p>\n<p><strong>+[PD=drainperiphery][PD=sourceperiphery][NRD=drainsquares]<\/strong><\/p>\n<p><strong>+[NRS=sourcesquares][NRG=gatesquares][NRB=bulksquares]<\/strong><\/p>\n<p><strong>+[OFF][IC=vds][,vgs[,vbs]]]<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2069 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-29.png\" alt=\"\" width=\"241\" height=\"260\" \/>\u00a0(29)<\/p>\n<p>Square brackets indicate that the quantity is optional. As an example, you might include a statement,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2090 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-Squarebrackets2V.png\" alt=\"\" width=\"556\" height=\"79\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-Squarebrackets2V.png 556w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiers6-Squarebrackets2V-300x43.png 300w\" sizes=\"auto, (max-width: 556px) 100vw, 556px\" \/><\/p>\n<p>This example specifies node numbers 1,2,3 and 0 for the drain, gate, source, and body of the device. Note that KP = 2<em>K <\/em>( = 2<em>I<sub>DSS<\/sub><\/em>\/<em>V<sub>P<\/sub><sup>2<\/sup><\/em>). Use PMOS for <em>p<\/em>-channel instead of NMOS in the second statement.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2093 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-3V.png\" alt=\"\" width=\"1154\" height=\"346\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-3V.png 1154w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-3V-300x90.png 300w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-3V-768x230.png 768w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-3V-1024x307.png 1024w\" sizes=\"auto, (max-width: 1154px) 100vw, 1154px\" \/><\/p>\n<p>The parameters, their default values and units, are given in Table 3. The model associated with these parameters is shown in Figure 30.<\/p>\n<div id=\"attachment_2074\" style=\"width: 469px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2074\" class=\"wp-image-2074 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-30.png\" alt=\"\" width=\"459\" height=\"257\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-30.png 459w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-30-300x168.png 300w\" sizes=\"auto, (max-width: 459px) 100vw, 459px\" \/><p id=\"caption-attachment-2074\" class=\"wp-caption-text\">Figure 30 \u2013 MOSFET transistor model<\/p><\/div>\n<p>&nbsp;<\/p>\n<div class=\"previous-page\"><a href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/6-comparison-of-mosfet-to-jfet\/\"><img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/leftarrow5.png\" \/>PREVIOUS- 6. Comparison of MOSFET to JFET<\/a><\/div>\n<div class=\"next-page\"><a style=\"font-size: 20px;\" href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/8-fet-amplifiers-canonical-configurations\/\">NEXT- 8. FET Amplifiers &#8211; Canonical configurations<img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/rightarrow5.png\" \/><\/a><\/div>\n<div class=\"clear\"><\/div>\n","protected":false},"excerpt":{"rendered":"<p>CURRENT &#8211; 7. FET Models for Computer Simulations PREVIOUS- 6. Comparison of MOSFET to JFET NEXT- 8. FET Amplifiers &#8211; Canonical configurations FET Models for Computer Simulations SPICE and MICRO-CAP contain sophisticated models for JFETs and MOSFETs. The JFET model (the SPICE 2G.6 model) contains 12 parameters. The MOSFET SPICE model contains 42 parameters in [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1764,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"yst_prominent_words":[145,150,143,151,113,148,141,159,128,126,149,85,142,158,131,152,147,140,144,146],"class_list":["post-2056","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2056","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/comments?post=2056"}],"version-history":[{"count":31,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2056\/revisions"}],"predecessor-version":[{"id":3461,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2056\/revisions\/3461"}],"up":[{"embeddable":true,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/1764"}],"wp:attachment":[{"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/media?parent=2056"}],"wp:term":[{"taxonomy":"yst_prominent_words","embeddable":true,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/yst_prominent_words?post=2056"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}