Author Topic: Resistors  (Read 2324 times)

seagreen

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Resistors
« on: June 25, 2010, 01:07:33 PM »
New topic (it even says so above):

I'm doing yet another home schooling project.  The student trying to learn is me.  This time, it's a power amplifier.

It would seem to me that the emitter resistors in the output stage are potentially a critical item.  They have to pass wide swings in applied current, which obviously dissipates power and causes thermal effects.  These thermal effects in turn will change the bias levels of the stage as the resistance changes in response to the power dissipation changes.  This effectively modulates the output stage.

In addition, the thermals probably generate 1/f noise in the resistor which also can modulate the output stage.

Any suggestions what to try as a decent resistor for this application?  Or am I just being stupid (again)?
No double blind testing was used in the making of this post.

Gen. Dreedle

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Re: Resistors
« Reply #1 on: June 25, 2010, 02:06:19 PM »
I know someone who used those TO-220 Caddock resistors. Plenty of dissipation. Especially if you heat sink them. Never tried it, though.

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seagreen

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Re: Resistors
« Reply #2 on: June 25, 2010, 02:35:05 PM »
Yeah, I thought about them.  I might end up with a heat sink as large as the one for the transistors.

Can't get Resistas.
Caddock MV234's?  But they're really hard to source.
Dale?
Mills "non-inductive" wire wound?
Give up?
No double blind testing was used in the making of this post.

tommy_t

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Re: Resistors
« Reply #3 on: June 25, 2010, 04:17:32 PM »
How about the old trick of using about four metal film resistors in parallel per output device?

seagreen

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Re: Resistors
« Reply #4 on: June 25, 2010, 05:56:05 PM »
That's certainly a good possibility.

I just didn't know if there was a proven solution.
No double blind testing was used in the making of this post.