[AMPS] 8877 Grid Dissipation

Fri, 8 Aug 1997 10:38:13 +0000

> To:            amps@contesting.com
> Date:          Fri, 8 Aug 97 05:28:12 +0000

> The total grid dissipation on a properly loaded 8877 amp running at
> 4000 volts and loaded to 800 ma plate current is 8.2 watts. Whether
> the maximum grid dissipation is 20 or 25 watts is not near as important
> as limiting the maximum grid current to 70-90 ma at all times

Amen.

Since the waveform is complex the grid dissipation can only 
be found by knowing the time integrated grid to cathode voltage and 
current over the whole RF cycle, but in a class AB2 GG PA it is about 
6-10 watts at normal output and drive levels with about 50 mA Ig.

It would be best to NEVER allow the Ig to exceed 100 mA, and 
NEVER operate the grid at any more current than absolutely necessary. 

Advice indicating the grid is "rugged" and will handle many amperes 
of grid current is VERY bad advice.

73 Tom

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm