{"id":6761,"date":"2017-09-22T20:51:55","date_gmt":"2017-09-22T19:51:55","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=6761"},"modified":"2017-09-22T20:51:55","modified_gmt":"2017-09-22T19:51:55","slug":"stop-that-oscillation-please","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2017\/09\/22\/stop-that-oscillation-please\/","title":{"rendered":"Stop that oscillation please!"},"content":{"rendered":"

I’ve been playing for some weeks the marvellous UV-201a stage<\/a>.  The addition of the source follower<\/a> brings a new dimension to this stage.  However, I experienced random oscillation on this setup. I knew it was the MOSFET, but I wanted to pin it down. <\/p>\n

I replaced the SiC version with the famous AOT1N60<\/a>. That cure the issue, but I wanted to find out what was going on, of course blaming my selection of gate stoppers. <\/p>\n

In case you were asking, how does the follower oscillation manifests? Well, simply like a random harsh noise on the background. You can tame it by restarting the HT supply, but that is a temporary workaround. <\/p>\n

The guilty bastard was the 1K\u03a9 carbon composition gate stopper. Here is what you get typically:<\/p>\n

\"\"A nice crest around 5-6Mhz. And this is the most stable, try the SiC MOSFET instead of the AOT1N60, it will go wild! <\/p>\n

So if you change the stoppers from 1K\u03a9 to simply 100\u03a9, this is what you get:<\/p>\n

\"\"<\/a><\/p>\n

And surprisingly, this is what you get with the C3M028009 SiC used before:<\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

My FR system can do better than this at 10Mz. A flat response all the way up, I like that.<\/p>\n

Doggy bag<\/h2>\n

Lesson learned: change the MOSFET enhancement mode stopper from 1K\u03a9 down to 100\u03a9 in a follower mode. Otherwise, it will go crazy!<\/p>\n

I will update the source follower documentation…<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve been playing for some weeks the marvellous UV-201a stage.  The addition of the source follower brings a new dimension to this stage.  However, I experienced random oscillation on this setup. I knew it was the MOSFET, but I wanted to pin it down.  I replaced the SiC version with the famous AOT1N60. That cure … Continue reading “Stop that oscillation please!”<\/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":[1029,1064,1062],"class_list":["post-6761","post","type-post","status-publish","format-standard","hentry","category-valves","tag-aot1n60","tag-bartola-source-follower-pcb","tag-source-follower-pcb"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1L3","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6761","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=6761"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6761\/revisions"}],"predecessor-version":[{"id":6765,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/6761\/revisions\/6765"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=6761"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=6761"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=6761"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}