On Wednesday 15 May 2013 11:24:49 John Kasunich did opine: > The current in that design is very dependent on transistor parameters > such as beta and Vbe that will change from part to part and with > temperature. Adding emitter resistor(s) stabilizes things. > > On Tue, May 14, 2013, at 10:39 PM, Przemek Klosowski wrote: > > On Tue, May 14, 2013 at 3:08 PM, Gene Heskett <[email protected]> wrote: > > > So it looks like I need to design a 10 amp constant current load, > > > switch mode of course. > > > > Perhaps something simpler? I have a sinking feeling that the > > electronics wizards will soon hand me my head on the platter but I > > think that the following circuit might work as a current load: it > > sets up a lousy voltage reference and uses it to trickle enough > > current into the base of a Darlington pair to drive the desired > > current through the load. > > --------------------------------------------------------------------- > > ---------
That PNG you sent has the sense R in the wrong leg of the transistor John, it should be in the emitter leg. Anyway, I just stumbled over some 400 volt, 15 amp darlington's at Jameco & I will build one bias circuit, feed two of those in parallel but with separate emitter R's in the .2 ohm range, $15 and change for 5 pieces by USPS first class. I looked at the heat sinks that had bugs on them, but they were 30 amp 45 volt PNP Germanium's, of little or no use here. I figure 2 of them sharing a heat sink about 5.5x10 x 2" tall, ought to handle that till the cows come home dripping. That heat sink also has a 6 pack of 1N3210 diodes on it, 15 amp 150 volt in a DO5 case, should make a nice bridge so this works in reverse too. ;-) Many thanks for the ideas everybody. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> Colors may fade in time. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ AlienVault Unified Security Management (USM) platform delivers complete security visibility with the essential security capabilities. Easily and efficiently configure, manage, and operate all of your security controls from a single console and one unified framework. Download a free trial. http://p.sf.net/sfu/alienvault_d2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
