{"id":6590,"date":"2017-07-30T09:58:12","date_gmt":"2017-07-30T08:58:12","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=6590"},"modified":"2017-07-30T09:58:12","modified_gmt":"2017-07-30T08:58:12","slug":"source-follower-pcb","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2017\/07\/30\/source-follower-pcb\/","title":{"rendered":"Source Follower PCB"},"content":{"rendered":"<p>I&#8217;ve been posting about the use of source followers in the circuits with some interesting results from testing. Some interesting posts to read, If you haven&#8217;t read them so far:<\/p>\n<ol>\n<li><a href=\"http:\/\/www.bartola.co.uk\/valves\/2015\/12\/21\/slew-rate-in-preamps\/\">Slew Rate<\/a>, <a href=\"http:\/\/www.bartola.co.uk\/valves\/2015\/12\/27\/slew-rate-part-2\/\">Slew Rate (Part 2),<\/a> <a href=\"http:\/\/www.bartola.co.uk\/valves\/2016\/01\/07\/slew-rate-part-iii\/\">Slew Rate (Part 3)<\/a>&nbsp;and <a href=\"http:\/\/www.bartola.co.uk\/valves\/2016\/01\/09\/slew-rate-part-iv-and-source-followers\/\">Slew Rate (Part 4)<\/a>.<\/li>\n<li><a href=\"http:\/\/www.bartola.co.uk\/valves\/2017\/06\/04\/6sf5-driver-for-300bgm70813-se-amps\/\">6SF5 driver for 300B\/GM70\/813 SE Amps<\/a><\/li>\n<li><a href=\"http:\/\/www.bartola.co.uk\/valves\/2017\/05\/29\/dht-phono-stage-test\/\">DHT Phono Stage Test<\/a>.&nbsp;<\/li>\n<\/ol>\n<p>After several tests over a variety of circuits, I finalised the prototype for a Source Follower PCB. The circuit is incredibly useful. Some examples of uses cases are:<\/p>\n<ul>\n<li>Amplifier output stage grid drive<\/li>\n<li>Screen drive amplifiers<\/li>\n<li>Screen voltage stabiliser for pentode stages<\/li>\n<li>HT voltage stabiliser for preamps<\/li>\n<li>Buffer stage for high-mu\/high-anode resistance stages &#8211; either triodes or pentodes (e.g. Phono)<\/li>\n<\/ul>\n<p>Some key aspects of the board are:<\/p>\n<ul>\n<li>The PCB has been designed to accommodate all sorts of power MOSFETs (both TO-220 and TO-247), in particular the high transconductance and low Crss ones which perform the best in this role.<\/li>\n<li>The tail CCS is simple and leverage the option of using same MOSFETs. &nbsp;&nbsp;<\/li>\n<li>The board takes into account the use of any bipolar supply up to 450V diferential. You only need to change a resistor depending on the supply voltage levels and make sure there is a sufficiently big heatsink on the MOSFETs.<\/li>\n<li>There is a current limiter circuit built in to protect screen or grid from excessive current. This is also very useful when the board is used as a voltage stabiliser for a preamp. You can limit the peak current and avoid destroying the MOSFETs when capacitors are charged or if accidentally the output is shorted. This circuit can be bypassed easily with a jumper.<\/li>\n<\/ul>\n<p>Here is one of the boards submitted to the usual abuse during testing:<\/p>\n<p><a href=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"6592\" data-permalink=\"https:\/\/www.bartola.co.uk\/valves\/2017\/07\/30\/source-follower-pcb\/sf-board-under-test\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg?fit=1224%2C1632&amp;ssl=1\" data-orig-size=\"1224,1632\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;2.2&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;iPhone 6&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;1501266252&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;4.15&quot;,&quot;iso&quot;:&quot;32&quot;,&quot;shutter_speed&quot;:&quot;0.03030303030303&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"SF board under test\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg?fit=768%2C1024&amp;ssl=1\" class=\"size-large wp-image-6592 aligncenter\" src=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test-768x1024.jpg?resize=525%2C700\" alt=\"\" width=\"525\" height=\"700\" srcset=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg?resize=768%2C1024&amp;ssl=1 768w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg?resize=225%2C300&amp;ssl=1 225w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test.jpg?w=1224&amp;ssl=1 1224w\" sizes=\"auto, (max-width: 525px) 85vw, 525px\" \/><\/a><\/p>\n<p>This is a very useful PCB in my view which can be used extensively in preamps, line stages and amplifiers.<\/p>\n<p>If there is sufficient interest, I will run a batch of PCBs for the DIY audio community:<\/p>\n<div data-test='contact-form'\n\t\t\tid='contact-form-6590'\n\t\t\tclass='jetpack-contact-form-container '\n\t\t\tdata-wp-interactive='jetpack\/form' 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href=\"\/valves\/wp-json\/wp\/v2\/posts\/6590\">\u2190 Back<\/a><\/p><h4 data-wp-bind--aria-hidden=\"state.isSuccessMessageAriaHidden\" id=\"contact-form-success-header-3b023d85c2a72e93464fb5055a26245d376ac2bc\">Thank you for your response. \u2728<\/h4>\n\n<template data-wp-each--submission=\"context.formattedSubmissionData\">\n\t\t\t\t\t<div class=\"jetpack_forms_contact-form-success-summary\">\n\t\t\t\t\t\t<div class=\"field-name-wrapper\">\n\t\t\t\t\t\t\t<div class=\"field-type-icon\" data-wp-watch=\"callbacks.watchFieldTypeIcon\"><\/div>\n\t\t\t\t\t\t\t<div class=\"field-name\" data-wp-text=\"context.submission.label\" data-wp-bind--hidden=\"!context.submission.label\"><\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<div class=\"field-value\" data-wp-text=\"context.submission.value\" data-wp-bind--hidden=\"!context.submission.showPlainValue\"><\/div>\n\t\t\t\t\t\t<a class=\"field-url\" data-wp-bind--href=\"context.submission.url\" data-wp-text=\"context.submission.value\" 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class=\"field-image-option__label-wrapper\">\n\t\t\t\t\t\t\t\t\t\t<span class=\"field-image-option__label-code\" data-wp-text=\"context.image.letterCode\"><\/span>\n\t\t\t\t\t\t\t\t\t\t<span class=\"field-image-option__label\" data-wp-text=\"context.image.label\" data-wp-bind--hidden=\"!context.image.label\"><\/span>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/template>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<div class=\"field-files\" data-wp-bind--hidden=\"!context.submission.files\">\n\t\t\t\t\t\t\t<template data-wp-each--file=\"context.submission.files\">\n\t\t\t\t\t\t\t\t<div class=\"field-file\">\n\t\t\t\t\t\t\t\t\t<div class=\"field-file__thumbnail\" data-wp-style--background-image=\"context.file.previewUrl\" data-wp-style--mask-image=\"context.file.iconUrl\" data-wp-bind--hidden=\"!context.file.hasPreview\"><\/div>\n\t\t\t\t\t\t\t\t\t<svg class=\"field-file__icon\" data-wp-bind--hidden=\"context.file.hasPreview\" width=\"20\" height=\"20\" viewBox=\"0 0 24 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PCB\"\n\t\t\t\tdata-wp-on--submit=\"actions.onFormSubmit\"\n\t\t\t\tdata-wp-on--reset=\"actions.onFormReset\"\n\t\t\t\tdata-wp-class--submission-success=\"context.submissionSuccess\"\n\t\t\t\tdata-wp-class--is-first-step=\"state.isFirstStep\"\n\t\t\t\tdata-wp-class--is-last-step=\"state.isLastStep\"\n\t\t\t\tdata-wp-class--is-ajax-form=\"context.useAjax\"\n\t\t\t\tnovalidate >\n<input type='hidden' name='jetpack_contact_form_jwt' 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data-wp-context='{\"fieldId\":\"g6590-country\",\"fieldType\":\"text\",\"fieldLabel\":\"Country\",\"fieldValue\":\"\",\"fieldPlaceholder\":\"\",\"fieldIsRequired\":\"1\",\"fieldErrorMessage\":\"\",\"fieldExtra\":[],\"formHash\":\"3b023d85c2a72e93464fb5055a26245d376ac2bc\"}'  class='grunion-field-text-wrap grunion-field-wrap'  data-wp-init='callbacks.initializeField' data-wp-on--jetpack-form-reset='callbacks.initializeField' >\n<label\n\t\t\t\tfor='g6590-country' class=\"grunion-field-label text\" >Country<span class=\"grunion-label-required\" 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Some interesting posts to read, If you haven&#8217;t read them so far: Slew Rate, Slew Rate (Part 2), Slew Rate (Part 3)&nbsp;and Slew Rate (Part 4). 6SF5 driver for 300B\/GM70\/813 SE Amps DHT Phono Stage Test.&nbsp; After &hellip; <a href=\"https:\/\/www.bartola.co.uk\/valves\/2017\/07\/30\/source-follower-pcb\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Source Follower PCB&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5],"tags":[1063,1061,1062],"class_list":["post-6590","post","type-post","status-publish","format-standard","hentry","category-valves","tag-sic-source-follower","tag-source-follower","tag-source-follower-pcb"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1Ii","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6590","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/comments?post=6590"}],"version-history":[{"count":5,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6590\/revisions"}],"predecessor-version":[{"id":6596,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6590\/revisions\/6596"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=6590"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=6590"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=6590"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}