jogas said:I need to reduce a -270 VDC down to -200 at 20 mA.
Is there any three pin component available?
Have you thought about just using a zener (or a string of zeners), resistor(s), and pnp transistor? A 70V drop across a transistor sinking 20mA is only 1.4W. You could also put a resistor in series with the collector to reduce the transistor's dissipation.
Re: Re: -200 VDC regulator
If your raw supply is floating you can use a pos regulator. Just ground the pos terminal and use the common terminal (which normally would be grounded) as the neg terminal. Works like a charm.
Jan Didden
jogas said:Hi,
I need to reduce a -270 VDC down to -200 at 20 mA.
Is there any three pin component available?
I only found a VB408 that is a positive regulator
Thanks in advance for your help
Giuseppe
If your raw supply is floating you can use a pos regulator. Just ground the pos terminal and use the common terminal (which normally would be grounded) as the neg terminal. Works like a charm.
Jan Didden
Poke around National Semiconductor's site. There's a nice paper by Michael Maida on using a HV bipolar to limit the voltage across a 317-type regulator. I think the paper is Linear Brief LB-47. This paper only shows positive regulators, but by using PNP (or p-channel FET), a 337, and turning around the diodes, you can make a negative regulator.
Or you could use the positive regulator as published inserted in the ground leg of your raw supply.
Or you could use the positive regulator as published inserted in the ground leg of your raw supply.
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