{"id":5039,"date":"2015-12-06T12:26:53","date_gmt":"2015-12-06T12:26:53","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=5039"},"modified":"2015-12-06T12:26:53","modified_gmt":"2015-12-06T12:26:53","slug":"gyrator-bias-discussion","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2015\/12\/06\/gyrator-bias-discussion\/","title":{"rendered":"Gyrator bias discussion"},"content":{"rendered":"

A very interesting point was raised on the 4P1L\u00a0DIYAudio thread<\/a> around the gyrator circuit using CCS and whether a simple resistor divider was better than the CCS due to the LND150 temperature drift.<\/p>\n

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

I’ve tried both options and I’d say I prefer the CCS despite the variation with temperature for the following reasons (which people\u00a0may well disagree):<\/p>\n

\"LND150<\/a><\/p>\n

    \n
  1. It’s true the LND150 varies a lot with temperature (see attached), however if it’s operated at low current (e.g.<500\u03bcA) the variation is small. In a cascoded pair for this circuit the drift in the output voltage is small. Simulated in Spice I get about 6.35mV\/\u00b0C. The resistor divider will be better of course but you need a smaller values to reduce impact of dR\/dT. This creates another problem which is the reduced PSR. With a compromise divider to balance idle current and PSR you can get 5 times less variation with temperature in the circuit under discussion – see below (e.g. 1.4mV\/\u00b0C)<\/li>\n
  2. For a smaller value of resistor divider the PSR is impacted and significantly lower than the CCS. If you don’t have a well filtered supply, the PSR benefits of the gyrator will be reduced due to this. For example, I did some quick comparisons by simulating my 01a preamp<\/a>. I used a 235K\u03a9\/220K\u03a9 and a 23K5\u03a9\/22K\u03a9 divider options with a typical film decoupling cap of 4.7\u03bcF.<\/li>\n<\/ol>\n

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

    The PSR of the CCS is above 100dB whilst the PSR of the resistor divider goes from 56dB (235K\u03a9\/220K\u03a9 divider) down to 37dB (23K5\u03a9\/22K\u03a9 divider).
    \nIn practice, I implemented two different circuits as I had a shunt regulator before when I had a resistor divider and now I don’t have any shunt regulator but I use the CCS version.<\/p>\n

    Looking at the output PSR as the gyrator provides additional rejection to noise. The resistor divider PSR is about 73dB and CCS is 30dB better anyway<\/p>\n

    \"01a<\/a><\/p>\n

     <\/p>\n

     <\/p>\n

     <\/p>\n

     <\/p>\n

     
    \nThe voltage variance is really small with temperature and this circuit in particular isn’t affected by such small drift in my view<\/p>\n","protected":false},"excerpt":{"rendered":"

    A very interesting point was raised on the 4P1L\u00a0DIYAudio thread around the gyrator circuit using CCS and whether a simple resistor divider was better than the CCS due to the LND150 temperature drift. I’ve tried both options and I’d say I prefer the CCS despite the variation with temperature for the following reasons (which people\u00a0may … Continue reading “Gyrator bias discussion”<\/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":[10,309,782,142,57,44,695],"class_list":["post-5039","post","type-post","status-publish","format-standard","hentry","category-valves","tag-01a","tag-01a-preamp","tag-4p1l","tag-4p1l-preamp","tag-ccs","tag-gyrator","tag-lnd150"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1jh","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5039","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=5039"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5039\/revisions"}],"predecessor-version":[{"id":5044,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5039\/revisions\/5044"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=5039"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=5039"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=5039"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}