{"id":2010,"date":"2018-05-04T11:14:30","date_gmt":"2018-05-04T11:14:30","guid":{"rendered":"https:\/\/www.tina.com\/resources\/?page_id=2010"},"modified":"2018-06-22T09:34:45","modified_gmt":"2018-06-22T09:34:45","slug":"6-comparison-of-mosfet-to-jfet","status":"publish","type":"page","link":"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/6-comparison-of-mosfet-to-jfet\/","title":{"rendered":"6. Comparison of MOSFET to JFET"},"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; 6. Comparison of MOSFET to JFET<\/div>\n<div class=\"previous-page\"><a href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/5-mosfet-integrated-circuits\/\"><img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/leftarrow5.png\" \/>PREVIOUS- 5. MOSFET Integrated circuits<\/a><\/div>\n<div class=\"next-page\"><a style=\"font-size: 20px;\" href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/7-fet-models-for-computer-simulations\/\">NEXT- 7. FET Models for computer simulations<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;\">Comparison of MOSFET to JFET<\/span><\/em><\/strong><\/p>\n<p>Before we see how to use the FET in an amplifier configuration, we pause to examine the essential similarity between the two broad classes of FET. We have considered the MOSFET in Section 2 and the JFET in Section 4. Within each class are the n-channel and p-channel devices. The MOSFET classification is further subdivided into enhancement and depletion transistors.<\/p>\n<h6><strong><em>These combinations lead to six possible types of devices:<\/em><\/strong><\/h6>\n<p>\u25cf The n-channel enhancement MOSFET (enhancement NMOS)<br \/>\n\u25cf The n-channel depletion MOSFET (depletion NMOS)<br \/>\n\u25cf The n-channel JFET<br \/>\n\u25cf The p-channel enhancement MOSFET (enhancement PMOS)<br \/>\n\u25cf The p-channel depletion MOSFET (depletion PMOS)<br \/>\n\u25cf The p-channel JFET<\/p>\n<p>Figure 28 summarizes the circuit symbols for these six types of devices. The arrows in the JFET symbol are sometimes moved to the Source terminal.<\/p>\n<div id=\"attachment_2026\" style=\"width: 521px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2026\" class=\"wp-image-2026 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-28.png\" alt=\"Circuit symbols for FETs\" width=\"511\" height=\"296\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-28.png 511w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersFigure6-28-300x174.png 300w\" sizes=\"auto, (max-width: 511px) 100vw, 511px\" \/><p id=\"caption-attachment-2026\" class=\"wp-caption-text\">Figure 28 &#8211; Circuit symbols for FETs<\/p><\/div>\n<p>A channel is created and the transistor is ON when the gate-to-source voltage breaks the threshold voltage (<em>V<sub>T<\/sub><\/em> for MOSFETs and <em>V<sub>p<\/sub><\/em> for JFETs). For the three <em>n<\/em>-channel devices, the channel is created when<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2028\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-33.png\" alt=\"\" width=\"98\" height=\"21\" \/>\u00a0(33)<\/p>\n<p>Alternatively, for the <em>p<\/em>-channel devices, the channel is created when<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2030\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-34.png\" alt=\"\" width=\"98\" height=\"21\" \/>\u00a0(34)<\/p>\n<p>The threshold is positive for the enhancement NMOS, the depletion PMOS, and the <em>p-<\/em>channel JFET. It is negative for the depletion NMOS, the enhancement PMOS, and the <em>n<\/em>-channel JFET.<\/p>\n<p>In order for the transistor to operate in the <em>triode region<\/em>, the drain-to-source voltage must obey the following inequalities:<\/p>\n<p>For <em>n<\/em>-channel MOSFETs or JFETs,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2031\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-35.png\" alt=\"\" width=\"116\" height=\"21\" \/>\u00a0(35)<\/p>\n<p>For <em>p<\/em>-channel MOSFETs or JFETs, the opposite is true. That is, to operate in the triode region,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2032\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-36.png\" alt=\"\" width=\"116\" height=\"21\" \/>\u00a0(36)<\/p>\n<p>In either case, if the inequality is not obeyed, the transistor operates in the saturation region when it is on.<\/p>\n<h6><strong><em>These relationships are summarized in Table 1.<\/em><\/strong><\/h6>\n<div id=\"attachment_2034\" style=\"width: 608px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2034\" class=\"wp-image-2034 size-full\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-1.png\" alt=\"\" width=\"598\" height=\"209\" srcset=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-1.png 598w, https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersTable6-1-300x105.png 300w\" sizes=\"auto, (max-width: 598px) 100vw, 598px\" \/><p id=\"caption-attachment-2034\" class=\"wp-caption-text\">Table 1 &#8211; FET Relationships<\/p><\/div>\n<p>We now show the similarity in the equations for drain current for the MOSFET and JFET. In the saturation region, the drain current for the MOSFET is [Equation 8 ( Chapter: &#8220;2. Metal-oxide semiconductor FET (MOSFET)&#8221; )],<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2036\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-37.png\" alt=\"\" width=\"172\" height=\"31\" \/>\u00a0(37)<\/p>\n<p>where <em>K<\/em> is given by,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2038\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-38.png\" alt=\"\" width=\"110\" height=\"40\" \/><\/p>\n<p>In the case of the JFET, the equivalent is [Equation 20 (Chapter: &#8220;3. Junction field-effect transistor (JFET)&#8221;)].<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2042\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-38V.png\" alt=\"\" width=\"177\" height=\"96\" \/>\u00a0(38)<\/p>\n<p>This is identical to the equation for the MOSFET if we set <em>V<sub>T<\/sub><\/em> equal to <em>V<sub>p<\/sub><\/em>, and equate the constants,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2044\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-39.png\" alt=\"\" width=\"62\" height=\"49\" \/>\u00a0(39)<\/p>\n<p>The same equivalence is true for the triode region. We presented the drain current equation for the MOSFET [see Equation 4 (Chapter: &#8220;2. Metal-oxide semiconductor FET (MOSFET)&#8221;]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2047\" src=\"https:\/\/www.tina.com\/resources\/wp-content\/uploads\/2018\/05\/Field-effectTransistorAmplifiersEq6-40.png\" alt=\"\" width=\"174\" height=\"29\" \/>\u00a0(40)<\/p>\n<p>This identical equation holds for the JFET with the substitution of <em>V<sub>p<\/sub><\/em> for <em>V<sub>T<\/sub><\/em>, and the value of <em>K<\/em> given in Equation (39).<\/p>\n<p>In summary, the only difference in the equations for the MOSFET and JFET are the values of the constant <em>K<\/em>, and the fact that the threshold voltage in the MOSFET is equivalent to the pinch-off voltage in the JFET.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"previous-page\"><a href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/5-mosfet-integrated-circuits\/\"><img decoding=\"async\" src=\"https:\/\/www.tina.com\/images\/resource\/leftarrow5.png\" \/>PREVIOUS- 5. MOSFET Integrated circuits<\/a><\/div>\n<div class=\"next-page\"><a style=\"font-size: 20px;\" href=\"https:\/\/www.tina.com\/resources\/home\/field-effect-transistor-amplifiers-2\/7-fet-models-for-computer-simulations\/\">NEXT- 7. FET Models for computer simulations<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; 6. Comparison of MOSFET to JFET PREVIOUS- 5. MOSFET Integrated circuits NEXT- 7. FET Models for computer simulations Comparison of MOSFET to JFET Before we see how to use the FET in an amplifier configuration, we pause to examine the essential similarity between the two broad classes of FET. We have considered the [&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":[133,132,130,129,113,136,134,135,137,128,126,85,131,109,59,138,127,140,139,77],"class_list":["post-2010","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2010","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=2010"}],"version-history":[{"count":38,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2010\/revisions"}],"predecessor-version":[{"id":3463,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/pages\/2010\/revisions\/3463"}],"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=2010"}],"wp:term":[{"taxonomy":"yst_prominent_words","embeddable":true,"href":"https:\/\/www.tina.com\/resources\/wp-json\/wp\/v2\/yst_prominent_words?post=2010"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}