From: Karl F. Larsen (firstname.lastname@example.org)
I think the operative word here, is who cares? Perhaps someone who needs
25 KW of power, but that's not QRP...:-) I learned about tubes in 1959 but
when I started working they handed me transistors like the 2n44 and said
make it work with these.
On Wed, 22 Aug 2001, Tony Fishpool wrote:
> I kind of remember it differently but it was over 20 years ago I last
> played with these things so I am willing to stand corrected.
> Isn't the DC bias derived from the fact that the cathode is raised above
> zero volts by the cathode resistor and is therefore positive with
> respect to the grid. Why? because the grid isn't drawing any current,
> and therefore even though the grid resistor is fairly large, there isn't
> any volts dropped across it and is therefore at zero volts - but more
> importantly, negative with respect to the cathode. (positive w.r.t. the
> cathode being a bad thing because it then becomes an anode!)
> You make sure that the bias point doesn't change with an AC input by
> adding a capacitor across the cathode resistor.
> <groan!> This was all too long ago :-)
> Kind regards
> Tony - G4WIF
> ----- Original Message -----
> From: <W2SH@aol.com>
> > Dave,
> > This was a useful tutorial.
> > Trusting only my memory, and without
> > taking the time to consult any written
> > references, I think that with grid leak bias
> > the voltage is developed from
> > the driving power across the grid resistor,
> > whereas the voltage developed
> > (usually across several megohms, as you
> > point out) by electrons striking the
> > grid on their way to the plate is called
> > contact potential bias.
-- Yours Truly,
- Karl F. Larsen, email@example.com (505) 524-3303 -
Search QRP-L Archives
QRP-L Archive |
[ 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 ]
This archive was generated by hypermail 2b29 on Fri Oct 05 2001 - 09:30:47 CDT