In Reply to: Hawksford current source? posted by Allen Wright on September 4, 2003 at 01:46:19:
I found the idea for a Hawksford CCS here on this audioasylum, it consist of adding a capacitor from the lower transistor's base to the upper's emitter.
Voltsecond has a webpage with it at:
http://www.siteswithstyle.com/VoltSecond/c4s_cascading_in_psu/C4S_cascading_in_psu.html
It's also known as a bootstrapped CCS from Kurt Strain.
http://db.AudioAsylum.com/cgi/m.pl?forum=tubediy&n=13763I did a simulation in B2 Spice with the different versions and here's their impedance:
-CCS with one BF872: 1.7 Meg
-CCS with two BF872 in cascode: 3.6 Meg
-CCS with two BF872 in Hawksford or bootstrapped cascode: 60.0 MegRegards,
Danny
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Follow Ups
- Re: Hawksford current source? - Danny T 15:29:27 09/04/03 (3)
- Thanks, Danny! - Allen Wright 02:20:21 09/05/03 (2)
- Another link - Gary P 05:09:44 09/05/03 (1)
- Gary can't find rev 4 and 5 on your pages.. nt - Bas Horneman 06:48:07 09/05/03 (0)