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
|