Multi-grid wrote:
On Dec 2, 8:02 pm, Ian Thompson-Bell wrote:
Ian Iveson wrote:
Don Pearce wrote
I have being playing around with plate characteristics
graphs, looking
at how basic parameters (gm,rp and mu) vary with operating
point. The
most frustrating thing about this is that the published
curves all
extend to rather large plate currents and voltages. For my
preamp I am
working at plate currents of less than 5mA and the curves
here are
rather cramped. Is there any source of curves that are
expanded for the
lower plate current region?
Cheers
Ian
It's a long, boring Sunday afternoon. Perfect time to do a
set of
measurements like this and post the results somewhere. If
this is an
area of valve performance that is poorly documented it
would be
interesting to know what kind of variation there is
between samples.
Surely if it were truly interesting it would be published
already?
That's what I would have thought. However, I expect manufacturers wanted
to show their products in the best possible light even in those days, so
bigger voltages, bigger currents and their consequent better mu and gm
figures would find their way onto the data sheets.

You might expect the published curves to cater for the
published typical operating conditions.
Ian, consider the output impedance of your stage, and make
sure your loadline is for actual AC operating conditions,
and not just whatever load resistor you are using. It may
become obvious that you need more current.
ra is about 10K and the anode resistor is 39K so the output impedance is
less than 10K. It feeds a load of 470K.

Ian
- Show quoted text -

hey-Hey!!!,
The large plate current curves can be scaled( that is calculate
different values for the Y-axis). I can't find the ref. that gives the
instructions...but when I do, you'll be the second one to know it.
cheers,
Douglas

Excellent. Looking forward to it.

Cheers

ian