{"id":5458,"date":"2019-04-02T05:45:06","date_gmt":"2019-04-02T11:45:06","guid":{"rendered":"http:\/\/play.fallows.ca\/wp\/?p=5458"},"modified":"2019-03-21T08:37:05","modified_gmt":"2019-03-21T14:37:05","slug":"dual-base-amplifier","status":"publish","type":"post","link":"https:\/\/play.fallows.ca\/wp\/projects\/electronics-projects\/dual-base-amplifier\/","title":{"rendered":"Dual Base Amplifier for Wideband Loops"},"content":{"rendered":"

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

My dual base amplifier is built to match remote wideband loops to a coherent two-channel receiver. Implemented with wideband FET op amps, performance is great.\u00a0<\/p>\n

As I learned to hot air solder SMD components, the dual base amplifier board was my third attempt. Surprisingly, the first time I powered it up, it worked perfectly.<\/p>\n

Check out the circuit described previously<\/a>. This board is designed to match signals from two remote wideband loops, using CAT transmission line, to a dual channel receiver. An RJ-45 connector (upper right) sends power to the head end amplifiers, and receives balanced signals from the loops.<\/p>\n

Basically, I designed an amplifier around the AD8067 high speed FET op amp<\/a> and built two of these onto one board. Power and receiver antenna connections are made using screw terminals. Otherwise, all the parts are surface mount.<\/p>\n

I thought this would be the hardest board to build. Fortunately, I had some practice before tackling. Hot air soldering actually works pretty well.<\/p>\n

As a side note, I was also able to use solder paste to hot air solder the eight pins on the RJ-45 connector. This seems to work okay when you have small pins that are very close to the board pads. Not so with the screw terminals, which needed through hole soldering.<\/p>\n

Dual Base Amplifier Initial Build Performance<\/h2>\n

You might be amazed at this, but my dual base amplifier performs exactly as LTSpice projected.<\/p>\n

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

The test was to feed a 50 mV signal at 10 MHz to Channel A input. Output was 364 mV peak-to-peak, for a gain of 21 dB. This was pretty much as modeled in LTSpice. Next I ran a frequency sweep from 100 kHz to 30 MHz. To my joy, gain was constant across most of the range, dropping off slightly above 25 MHz.<\/p>\n

You can see input (yellow), output (blue) and FFT in the picture above.<\/p>\n

Current drain was 13 mA for the dual base amplifier, just as predicted with the LTSpice model.<\/p>\n

By the way, EasyScopeX<\/a> software does a great job of capturing screen graphics from my Siglent 1052 digital oscilloscope<\/a>. The FFT function is particularly useful.<\/p>\n","protected":false},"excerpt":{"rendered":"

My dual base amplifier is built to match remote wideband loops to a coherent two-channel receiver. Implemented with wideband FET op amps, performance is great.\u00a0<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"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":"","_share_on_mastodon":"0"},"categories":[11],"tags":[246,239,202,95,22],"series":[312],"class_list":["post-5458","post","type-post","status-publish","format-standard","hentry","category-electronics-projects","tag-hamr","tag-hamradio","tag-magloop","tag-pcb","tag-swl","series-implementing-wideband-loop-vision"],"yoast_head":"\nDual Base Amplifier for Wideband Loops - Making It Up<\/title>\n<meta name=\"description\" content=\"My dual base amplifier is built to match remote wideband loops to a coherent receiver. 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