{"id":8916,"date":"2020-10-17T12:01:22","date_gmt":"2020-10-17T11:01:22","guid":{"rendered":"https:\/\/www.bartola.co.uk\/valves\/?p=8916"},"modified":"2020-10-17T12:01:22","modified_gmt":"2020-10-17T11:01:22","slug":"fixed-bias-board","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2020\/10\/17\/fixed-bias-board\/","title":{"rendered":"Fixed Bias Board"},"content":{"rendered":"

Long time ago I built a series variable voltage regulator for 600V. It worked flawlessly and survived all sorts of abuses as is on my bench HT supply.<\/p>\n

With the same circuit design, I developed the final stackable PCB (see previous post here<\/a>) with this regulator:<\/p>\n

\"\"<\/a>
HV Series Variable Voltage Regulator<\/figcaption><\/figure>\n

Looks more complicated than it is. The single-supply Op Amp (LM358) needs a low voltage supply. I derived this from a simple CCS (DN2540) and a pair of 12V Zener diodes. The voltage reference is the famous TL431A and with P1 you can adjust the output voltage. The feedback resistor pair (R14 and R15) senses the output. C6 is for frequency compensation. The MOSFETs used are ST3LN80K5 which have built in protection Zener diodes, so none of the ones shown in the diagram are actually needed. T4 provides current protection to the pass device T2.<\/p>\n

<\/p>\n

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

According to the LT Spice simulations, it should have about 80dB at 100Hz. I could only measure 50dB as my bench noise was about 300\u03bcV and input ripple was low already. I should test it further.<\/p>\n

Anyhow, the other interesting test I made was to develop a 60-90V bias circuit from a 12V input. I used the cheap SMPS Chinese modules fed from 12V (100mA) into an RC circuit at the output (470R\/100\u03bcF) before feeding the voltage regulator. Was nice to see the rock solid output at 70V and same 300\u03bcV noise. \u00a0I was thinking of using this approach to generate the fixed bias of the RL12P35 SE Amp \u2013 part I<\/a> amplifier. In this way I could get away from a negative supply and generate the bias from the heater supply. Not sure how reliable this would be, perhaps won’t do it at all.<\/p>\n

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

Long time ago I built a series variable voltage regulator for 600V. It worked flawlessly and survived all sorts of abuses as is on my bench HT supply. With the same circuit design, I developed the final stackable PCB (see previous post here) with this regulator: Looks more complicated than it is. The single-supply Op … Continue reading “Fixed Bias Board”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_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},"jetpack_post_was_ever_published":false},"categories":[5],"tags":[401,1379,1378],"class_list":["post-8916","post","type-post","status-publish","format-standard","hentry","category-valves","tag-fixed-bias","tag-hv-voltage-regulator","tag-variable-series-hv-regulator"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-2jO","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8916","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=8916"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8916\/revisions"}],"predecessor-version":[{"id":8919,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8916\/revisions\/8919"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=8916"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=8916"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=8916"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}