[Amps] A Grounded Grid biasing question

[TexasRF at aol.com]

Marv, I have used this method in several grounded grid tetrode amplifiers  
with excellent results. There is an added advantage that a big diode can be  
placed from B- (cathode) and ground to snub any big voltages on the cathode that  
might happen during a plate to ground flashover event.
 
Not only will the diode protect the tube but also the grid and plate  
metering circuits.
 
When you design the grid bias circuit, keep in mind that peak grid  current 
will be many times the indicated average current. I have used  smallish zener 
diodes connected to a potentiometer and emitter follower circuit  with good 
results in this application.
 
73,
Gerald K5GW
 
 
 
 
In a message dated 7/9/2008 11:45:14 A.M. Central Daylight Time,  
wc6w_amps at yahoo.com writes:

Has anyone ever seen a design wherein an 8877, or similar triode, operated in 
 grounded grid has the bias generator placed in the grid return line, rather  
than in the typical cathode (grid + cathode current) location?   

This implies that the HV return must be allowed to float at  least as 
positive as the bias value. The grid remains chassis grounded as  usual.  And the 
advantage of this arrangement is that the bias generator  need only pass the grid 
current which is typically 1/10 of the cathode  current.

A proposed circuit may be seen  at:

http://wc6w.50webs.com/wc6wamps/index.html?fr40.html

73  & Good morning,
Marv WC6W  

http://wc6w.50webs.com/




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