{"id":2975,"date":"2024-08-25T22:09:48","date_gmt":"2024-08-25T22:09:48","guid":{"rendered":"https:\/\/workhouse.sweetdishy.com\/?p=2975"},"modified":"2024-08-25T22:09:48","modified_gmt":"2024-08-25T22:09:48","slug":"not-and-buf-gates","status":"publish","type":"post","link":"https:\/\/workhouse.sweetdishy.com\/index.php\/2024\/08\/25\/not-and-buf-gates\/","title":{"rendered":"Not and BUF Gates"},"content":{"rendered":"\n

The simplest logic function to implement in CMOS is a NOT gate (Figure 10.20). The small circle, or bobble, on the control input of transistor Tr1<\/sub>\u00a0indicates a PMOS transistor. The bobble is used to indicate that this transistor has an active-low control, which means that a logic 0 applied to the control input turns the transistor ON and a logic 1 turns it OFF. The lack of a bobble on the control input of transistor Tr2<\/sub>\u00a0indicates an NMOS transistor. The lack of a bobble says that this transistor has an active-high control, which means that a logic 1 applied to the control input turns the transistor ON and a logic 0 turns it OFF.<\/p>\n\n\n\n

\"image\"\/<\/figure>\n\n\n\n

Figure 10.20<\/strong> CMOS implementation of a NOT gate<\/p>\n\n\n\n

Thus, when a logic 0 is applied to input a<\/em>, transistor Tr1<\/sub> is turned ON, transistor Tr2<\/sub> is turned OFF, and output y<\/em> is connected to logic 1 via Tr1<\/sub>. Similarly, when a logic 1 is<\/a> applied to input a<\/em>, transistor Tr1<\/sub> is turned OFF, transistor Tr2<\/sub> is turned ON, and output y<\/em> is connected to logic 0 via Tr2<\/sub>.<\/p>\n\n\n\n

Don\u2019t worry if all this seems a bit confusing at first. The main points to remember are that a logic 0 applied to its control input turns the PMOS transistor ON and the NMOS transistor OFF, while a logic 1 turns the PMOS transistor OFF and the NMOS transistor ON. It may help to visualize the NOT gate\u2019s operation in terms of switches rather than transistors (Figure 10.21).<\/p>\n\n\n\n

\"image\"\/<\/figure>\n\n\n\n

Figure 10.21<\/strong> NOT gate\u2019s operation represented in terms of switches<\/p>\n\n\n\n

Surprisingly, a non-inverting BUF gate is more complex than an inverting NOT gate. This is due to the fact that a BUF gate is constructed from two NOT gates connected in series (one after the other), which means that it requires four transistors (Figure 10.22).<\/p>\n\n\n\n

\"image\"\/<\/figure>\n\n\n\n

Figure 10.22<\/strong> CMOS implementation of a BUF gate<\/p>\n\n\n\n

The first NOT gate is formed from transistors Tr1<\/sub> and Tr2<\/sub>, while the second is formed from transistors Tr3<\/sub> and Tr4<\/sub>. A logic 0 applied to input a<\/em> is inverted to a logic 1 on w<\/em>, and then inverted back again to a logic 0 on output y<\/em>. Similarly, a logic 1 on a<\/em> is inverted to a logic 0 on w<\/em>, and then inverted back again to a logic 1 on y<\/em>.<\/a><\/p>\n\n\n\n

Around this stage it is not unreasonable to question the need for BUF gates in the first place\u2014after all, their logical function could be achieved using a simple piece of wire. But there\u2019s method to our madness, because BUF gates may actually be used for a number of reasons: for example, to isolate signals, to provide increased drive capability, or to add an element of delay.<\/p>\n","protected":false},"excerpt":{"rendered":"

The simplest logic function to implement in CMOS is a NOT gate (Figure 10.20). The small circle, or bobble, on the control input of transistor Tr1\u00a0indicates a PMOS transistor. The bobble is used to indicate that this transistor has an active-low control, which means that a logic 0 applied to the control input turns the […]<\/p>\n","protected":false},"author":1,"featured_media":2976,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[417],"tags":[],"class_list":["post-2975","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-digital-electronics"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/08\/circuit.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2975","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=2975"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2975\/revisions"}],"predecessor-version":[{"id":2977,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2975\/revisions\/2977"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/2976"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=2975"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=2975"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=2975"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}