Plus it allows for all kinds of interesting test scenarios.
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13 years ago
300W Resistive load?
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13 years ago
Unless it was slightly less old and used TO-3 MOSFETs, which Idunno, might be worth something on eBay. :^)
handle the voltage just fine, as long as there's enough for the power.
I had one power BJT per FACE... 400W audio amplifier ;-) ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 |
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13 years ago
I still fail to see why it wouldn't work. The only failure mode I can think of is the case in which the emitter resistors are too small to divide the load properly at low currents / high voltages.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
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13 years ago
Not saying it cannot work, but you'd need big expensive transistors to make an active load for 200V at hundreds of watts.
I'm working on a power DAC at the moment, only going up to about 30V and 30A, non-trivial when you want the same circuit to hold to the output to nearest mV or mA ;)
First version with transistors leaked and drifted too much, current version being designed & built with MOSFET switched resistor banks and analog power amp to make up the small stuff seems far more viable.
But here I'm drifting OT as I'm making a precision load, not a simple test load, but that explains why my focus is more on the reliability of an active load.
Recently I built a 1A current sink, while it didn't fail, it was cooking a power MOSFET on large heatsink, but without fan, at only 30W. So I pulled the plug at 20 hours operation. Then realised I could use a bridge circuit instead of accurate current sink. Side stepped a problem, finding a better solution :) I ordered $5 worth of precision resistors 10:1 ratio.
Grant.
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13 years ago
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che_mode
So either the transistors seems to avalanche, i.e. current goes way = higher than expected, or voltage starts pulling down, or it burns out = altogether.
Tim
--=20 Deep Friar: a very philosophical monk. Website:
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13 years ago
On Tue, 20 Jul 2010 23:24:52 -0500, "Tim Williams" = put together some random words that came up with:
nche_mode
higher than expected, or voltage starts pulling down, or it burns out = altogether.
I used a 220V electric water heater element for a load when I build a = power supply for an argon laser. It worked great.
Steve