LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #1   Report Post  
Old November 4th 06, 06:34 PM posted to rec.radio.amateur.homebrew
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 47
Default Class C amps and saturation (again)

Back in July I wrote:

I'm reading David Rutledge's excellent "The Electronics of Radio."
In Chapter 10 -- Power Amplifiers, he discusses Class C amps and says,
"In addition, if we drive the transistor clear to saturation, using the

transistor as a switch, the dissipated power can be greatly reduced,
because the saturation voltage is low. This is Class C
amplification..."
I'd always throught that in Class C, while you'd operate the device so
that it was cutoff during most of the cycle, but not saturated.
Is this just a different definition of Class C?
I checked back with SSDRA and EMRFD, and didn't see anything about
driving Class C amps into saturation?
What says the group? Do we saturate in Class C or not?
--------------------------------------------------------
I've been thinking about this some more. The 1980 ARRL handbook points
out that "Solid State power amplifiers should be operated just below
their saturation points for best efficiency and stability." Also, the
formula that we use to determine load resistance (Rl=Vcc^2/2Po) implies
that we are looking for a combination of Vcc, Load resistance and power
out that will prevent saturation.
And wouldn't we end up with far lower harmonic content if we only clip
one side of the wave form (at cutoff) instead of both sides (cutoff and
saturation)?

I know there are more exotic modes beyond C, but for plain old ordinary
ham radio applications, don't we normally avoid saturation in Class C
amps?

Also, what about this business of having the efficiency improve through
saturation "because the saturation voltage is low" Could that be
right? If you put a voltage across a conductor and generate a large
current, you can't sit back and say "Great! Power consumption across
the conductor is low because the voltage drop across it is now
minimal!"

73 from London
Bill M0HBR N2CQR CU2JL
http://www.gadgeteer.us

 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
SolderSmoke #28: SPRAT, QRSS, QST $50 RIG, Class C saturation? A Logo for SolderSmoke [email protected] Homebrew 9 September 13th 06 12:32 AM
Class C amps saturating? [email protected] Homebrew 20 August 9th 06 07:58 PM
SolderSmoke #28: SPRAT, QRSS, QST $50 RIG, Class C saturation? A Logo for SolderSmoke [email protected] Boatanchors 0 August 5th 06 07:03 AM
SolderSmoke #28: SPRAT, QRSS, QST $50 RIG, Class C saturation? A Logo for SolderSmoke [email protected] Equipment 0 August 5th 06 07:03 AM
SolderSmoke #28: SPRAT, QRSS, QST $50 RIG, Class C saturation? A Logo for SolderSmoke [email protected] General 0 August 5th 06 07:03 AM


All times are GMT +1. The time now is 06:33 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017