{"id":7318,"date":"2018-03-30T17:48:04","date_gmt":"2018-03-30T16:48:04","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=7318"},"modified":"2018-03-30T17:48:04","modified_gmt":"2018-03-30T16:48:04","slug":"tracing-mosfets-to-be-used-in-the-gyrator-pcb","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2018\/03\/30\/tracing-mosfets-to-be-used-in-the-gyrator-pcb\/","title":{"rendered":"Tracing (MOS)FETs to be used in the gyrator PCB"},"content":{"rendered":"

I took out the Locky Tracer and remove some dust, it was about time. One of the most popular lower FETs I use in the gyrator PCB<\/a> is the now obsolete BF862. Here is the tracing output:<\/p>\n

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

You can see that for a typical preamp stage where the DHT has an anode current from 5 to 15mA, the transconductance is 30mS to 40mS. This yield an \u00a0output impedance of 30\u03a9 down to 25\u03a9 in a hybrid mu-follower stage.<\/p>\n

Now, we can look at the enhancement MOSFETs which I introduced long time ago: BSH111BK or BSN20K:<\/p>\n

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

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

Both devices behave similarly at low voltage and current. Despite the BSN20BK has higher transconductance at large current, when we look at both of them below 30mA, you can see that they are not far off. \u00a0Even at 5mA they have higher transconductance than the BF862 (50mS versus 30mS). This will yield an even lower output impedance.<\/p>\n

Now, let’s look at the top devices.<\/p>\n

One of the reasons why I introduced the IXTP08N100D was that as a top device in a cascode pair can provide a higher VDS headroom to the lower device given the VGS behaviour compared to the DN2540. Below is the clear evidence. Let’s pick 20mA for example. The DN2540 will bias the lower device VDS at about 1.4V. On the contrary the IXT08N100D will provide 2.0V of VDS. This will yield a better frequency response of the hybrid mu-follower stage as the FET capacitances are minimised the higher the VDS voltage is.<\/p>\n

Now, have a look at the IXTP3N100D<\/a>, which can deliver 3A!. It has an even better VGS curve than the 08N100D. \u00a0Adding this device as the top MOSFET in the gyrator PCB will deliver an even better frequency response.<\/p>\n

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

Now, it’s time for matching FETs for my new RIAA project. \ud83d\ude42<\/p>\n

Stay tuned<\/p>\n

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

I took out the Locky Tracer and remove some dust, it was about time. One of the most popular lower FETs I use in the gyrator PCB is the now obsolete BF862. Here is the tracing output:<\/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":[911],"tags":[777,875,1140,850,1141,1142],"class_list":["post-7318","post","type-post","status-publish","format-standard","hentry","category-gyrator-pcb","tag-bf862","tag-gyrator-pcb","tag-ixt3n100d","tag-ixtp08n100d","tag-ixys-mosfets","tag-tracing-mosfets"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1U2","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7318","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=7318"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7318\/revisions"}],"predecessor-version":[{"id":7326,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7318\/revisions\/7326"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=7318"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=7318"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=7318"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}