Possible improvements for Aleph? - Page 8 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 20th May 2009, 03:03 PM   #71
The one and only
Nelson Pass's Avatar
Join Date: Mar 2001
Originally posted by kenpeter
Yet another glorious distraction! Like you didn't see one coming.

Quasi Complimentary Opto-Alephs?
I did not see that one coming.

  Reply With Quote
Old 20th May 2009, 10:30 PM   #72
diyAudio Member
Join Date: Nov 2007
Location: Dallas
Not the fastest way to abuse an optocoupler...
Been reading up on how to stretch opto bandwidth.

We can cascode the collectors to hide Miller, but there
ain't really enough voltage between gate and source
in this application to squeeze such a cascode.

We can use just collector-base junction as photodiode.
Thats very fast, but then you still have to amplify it...

Easiest cheat might be 47K ~ 470K bleeder from base
to emitter. Lose some gain, but shuts down quicker...
Letting bases float as I did, the sure ticket to slowville.

And obviously the whole thing needs some diamond
style buffering to get the input impedance up. Easy.
  Reply With Quote
Old 10th June 2009, 11:15 PM   #73
diyAudio Member
Join Date: Nov 2007
Location: Dallas
Another screwy idea: Did not exactly improve the thing I was
shooting to fix. (Drive bandwidth can't make 20KHz rail to rail),
but still might be of lame slackademic interessence or whatnot...
I'm still working on the original problem.

JFETs didn't work better than bipolars as comparators. But in
this case, matched sums (from matched pairs) make voltage
spanned across the input buffers equal. Toshiba 2sk389/2sk
109 matched pairs. I abuse the models for 2sk170/2sj74 as
JFET singles. It seemed plausible...

Equal, but not necessarily right. Got to jigger with resistors
to equalize thresholds at the MOSFET gates. Inequality is
almost assured. And mind you, the thresholds of the JFET
comparators have to be significantly less than thresholds
of the MOSFETs to be controlled.

Whatever else, the input impedance increase seems useful.
Attached Images
File Type: gif jfork1.gif (55.8 KB, 192 views)
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Improvements to first GC hotscot Chip Amps 1 26th December 2008 07:09 AM

New To Site? Need Help?

All times are GMT. The time now is 07:22 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2