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Re: [Amps] RF power transistor curve trace question

Subject: Re: [Amps] RF power transistor curve trace question
From: Manfred Mornhinweg <>
Date: Sun, 14 Jun 2009 20:55:47 +0000
List-post: <">>
Hi Dan,

> When placed in the curve tracer it produces a pattern with almost 
> horizontal trace, based step. 

What are you tracing, exactly? Collector current versus base voltage, or 
what? At what collector voltage, etc?

 >I removed the devices from one of the ENI
> boards and checked the curves . They were rising with a pattern of 
> between 0 and about 15 degrees, significantly different pattern. (the 
> gain was close.)
> What determines the 'slope' in an RF power transistor?

I would think that the first transistor you traced isn't nearly as 
heavily ballasted as the second. But I can't be sure if I don't know 
exactly what you are tracing!

> What is its significance?

If the difference is the ballasting, then basically it means the "flat" 
transistor is suitable for class-C service only, while the "non-flat" 
one is suitable for linear service too.

If a transistor with no or not enough ballasting is used in linear 
service, it will typically burn out from hotspotting.


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