[AMPS] Conjugate Matching In Class B and C Amplifiers

[Billy Ward]

Thanks for your words!

I am not the least in disagreement with what you are saying.  I would have 
to look at the wording that I used originally in my post.  I meant to say 
that a simultaneous conjugate match insured stability--not that it was 
required.  And, of course, I assumed that anyone that understood the term CM 
would know that it was only at a given frequency.

Billy Dean Ward


>From: Jon Ogden <na9d@speakeasy.net>
>To: Billy Ward <billydeanward@hotmail.com>, <amps@contesting.com>
>Subject: Re: [AMPS] Conjugate Matching In Class B and C Amplifiers
>Date: Wed, 16 May 2001 10:22:50 -0500
>
>on 5/16/01 9:51 AM, Billy Ward at billydeanward@hotmail.com wrote:
>
> >> Conjugate matching is not required for unconditional stability.    
>That's
> >> incorrect.  Many low noise amplifiers are purposely mismatched because
> >> simultaneous conjugate match generally does not equal minimum noise 
>figure.
> >
> > I was not taking minimum noise figure into the context of what I said.  
>I am
> > willing to learn.  I purposely mismatch for best noise figure. in 
>low-level
> > stages, also. However, I am curious how that makes my statement 
>incorrect
> > that Conjugate Matching is not required for unconditional stability.
>
>A simultaneous conjugate match is unconditionally stable.  However, any
>other match may be unconditionally stable as well.
>
>Unconditional stability is not just so simple as defining a match at one
>frequency.  After all, the conjugate match is technically going to exist
>over a relatively narrow band for the most part (most of what we do is
>narrow band).  Certainly, if I match an amplifier for a conjugate match at
>14 MHz, it will NOT be conjugately matched at 28 MHz.   Is the amp unstable
>then?  Perhaps, perhaps not.
>
>Many of us when testing linears for stability, test them with open circuits
>on the input and output when keying down.  We rotate the tank circuit
>through various positions to test for stability.  Certainly, this is not a
>conjugate matching system either, yet if an amplifier is properly designed,
>it will be stable.
>
>Simultaneous conjugate match insures stability at the frequency of the
>match, but not anywhere else.  It is NOT a condition for stability.
>
>I'll comment on the rest of your post at a later time, if someone else
>doesn't beat me to it.  I hope W8JI comments on it.
>
>73,
>
>Jon
>NA9D
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Member:  ARRL, AMSAT, DXCC, NRA
>
>http://www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>

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