Gainclone driving inductive loads

diyman · 11th April 2004, 06:55 PM

Has anyone tried using gainclone chips LM3875/2875 to drive small inductive loads? I'm thinking using one to drive a small 30VA toroid transformer in a power regeneration project.

ckt

adx · 12th April 2004, 09:53 AM

I've done similar things. It should work well, an inductive load is a naturally easy load for an amplifier chip. The chips are overcurrent and overtemperature limited so they are reasonably robust.

A couple of caveats:

I ran into HF oscillation problems - normal GC precautions (Zobels, not running at low gain, short FB path etc) should see it work well.

Watch out for the low DC resistance of the transformer. Even a small offset voltage will cause a reasonable DC current to flow, and toroids saturate very easily. Some way of tweaking out the offset might help (see National appnotes).

11th April 2004, 06:55 PM	#1
diyman diyAudio Member Join Date: Nov 2001 Location: Malaysia	Gainclone Has anyone tried using gainclone chips LM3875/2875 to drive small inductive loads? I'm thinking using one to drive a small 30VA toroid transformer in a power regeneration project. ckt

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12th April 2004, 09:53 AM	#2
adx diyAudio Member Join Date: Mar 2004 Location: Christchurch	I've done similar things. It should work well, an inductive load is a naturally easy load for an amplifier chip. The chips are overcurrent and overtemperature limited so they are reasonably robust. A couple of caveats: I ran into HF oscillation problems - normal GC precautions (Zobels, not running at low gain, short FB path etc) should see it work well. Watch out for the low DC resistance of the transformer. Even a small offset voltage will cause a reasonable DC current to flow, and toroids saturate very easily. Some way of tweaking out the offset might help (see National appnotes).

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