Billy/John,
I am not sure it even makes sense to talk about conjugate matching and
unconditional stability. Unconditional stability implies that an amplifier
is stable for all combinations of positive resistance input and output load
impedances, whereas conjugate matching implies a single pair of input and
output impedances. Of course, since input impedance termination can effect
output impedance and vice versa, there may be a loci of input/output
impedances
pairs which produce a simultaneous input and output conjugate match, but this
loci certainly wouln't include the whole 2 dimensional input/ouput impedance
state space of all possible combinations of input and output impedances with
positive real components as implied by unconditional stability.
73 de Mike, W4EF.............................
----- Original Message -----
From: "Jon Ogden" <na9d@speakeasy.net>
To: "Billy Ward" <billydeanward@hotmail.com>; "Amps Reflector"
<amps@contesting.com>
Sent: Tuesday, May 15, 2001 8:42 PM
Subject: Re: [AMPS] Conjugate Matching In Class B and C Amplifiers
>
> on 5/15/01 4:45 PM, Billy Ward at billydeanward@hotmail.com wrote:
>
> > Linear Amplifiers may or may not be conjugately matched. For maximum power
> > transfer to occur both in and out, and for the amplifier to be
> > unconditionally stable, there must be a simultaneous conjugate match.
> > This is not always easy as the input match affects the input match and visa
> > versa. However, it CAN be done.
>
> 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.
>
> Unconditional stability is determined by K factor of Linville's theorem (if
> I remember the name correctly, it's been a while.).
>
> Additionally, adjusting input match does not necessarily always affect the
> output match and vice versa. I am trying to think whether or not your
> statement is correct. Too many cobwebs upstairs right now.
>
> Generally speaking of this subject, I had always thought that the efficiency
> of an amplifier and whether or not you simulataneously match it were
> independent. It wasn't until coming onto this reflector and reading stuff
> from the likes of Dick Erhorn that some people feel that a conjugate match
> guarantees 50% efficiency or less.
>
> Of course, since my schooling and most of my work life revolved around class
> A amplifiers, I never thought about efficiency anyhow, since it's poopy in a
> class A amp anyhow.
>
> So some people here showed me the view on efficiency being 50% or less; I
> stated it in an earlier post; Tom Rauch says that is incorrect. I haven't
> had the time to go back to my textbooks and look at what they say.
>
> 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."
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|