A PLL frequency synthesizer has a reference frequency of 25 kHz. The frequency divider is set to a factor of 345. What is the output frequency?<\/p>\n\n\n\n
The correct answer and explanation is :<\/strong><\/mark><\/p>\n\n\n\n To find the output frequency of a PLL (Phase-Locked Loop) frequency synthesizer<\/strong>, we use the basic formula:<\/p>\n\n\n\n $$ Where:<\/p>\n\n\n\n $$ A PLL (Phase-Locked Loop) frequency synthesizer<\/strong> is an electronic system used to generate a range of frequencies from a fixed reference frequency. It is widely used in radio, telecommunications, and clock generation in digital systems due to its ability to provide stable and programmable output frequencies.<\/p>\n\n\n\n At the heart of the PLL is a phase detector<\/strong>, a low-pass filter<\/strong>, a voltage-controlled oscillator (VCO)<\/strong>, and a feedback divider<\/strong>. The system locks the VCO’s output frequency in phase and frequency with the reference signal. This is achieved by comparing the phase of the reference frequency $f_{\\text{ref}}$ with a divided version of the output signal $f_{\\text{out}}$, typically divided by an integer factor $N$.<\/p>\n\n\n\n When locked, the output frequency of the VCO is:<\/p>\n\n\n\n $$ In this case, the PLL uses a reference frequency of 25 kHz<\/strong>. The feedback divider is set to 345<\/strong>, meaning the VCO output must be 345 times higher than the reference frequency for the loop to be in lock.<\/p>\n\n\n\n Thus, the output frequency becomes:<\/p>\n\n\n\n $$ This principle allows PLLs to generate high frequencies from low-frequency stable references (such as a crystal oscillator), with fine control over the output by simply adjusting the divider factor $N$. It’s particularly valuable for generating clock signals in digital circuits or carrier signals in RF systems.<\/p>\n","protected":false},"excerpt":{"rendered":" A PLL frequency synthesizer has a reference frequency of 25 kHz. The frequency divider is set to a factor of 345. What is the output frequency? The correct answer and explanation is : To find the output frequency of a PLL (Phase-Locked Loop) frequency synthesizer, we use the basic formula: $$f_{\\text{out}} = N \\cdot f_{\\text{ref}}$$ […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-210811","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/210811","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=210811"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/210811\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=210811"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=210811"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=210811"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
f_{\\text{out}} = N \\cdot f_{\\text{ref}}
$$<\/p>\n\n\n\n\n
\n\n\n\nGiven:<\/strong><\/h3>\n\n\n\n
\n
f_{\\text{out}} = 345 \\times 25\\ \\text{kHz} = 8,625\\ \\text{kHz} = \\boxed{8.625\\ \\text{MHz}}
$$<\/p>\n\n\n\n
\n\n\n\nExplanation (Approx. 300 words):<\/strong><\/h3>\n\n\n\n
f_{\\text{out}} = N \\cdot f_{\\text{ref}}
$$<\/p>\n\n\n\n
f_{\\text{out}} = 25,000\\ \\text{Hz} \\times 345 = 8,625,000\\ \\text{Hz} = \\boxed{8.625\\ \\text{MHz}}
$$<\/p>\n\n\n\n