6—6.
THE MUTUAL CONDUCTANCE gm
123
6—6.
The Mutual Conductancè g….—The mutual conductance
g…, or as it is sometimes called, the trans—conduCtance &… expressed
in.mhos, is dened asthe change of plate current per volt change
on the grid. Thus,
_
,
'
'
.
.
___
___.
.
_
6—12
_
It is a measure of the
of. voltage
the
grid in causing changes in the plate current. Dividing equation
6—3 by 6—10 shows that
_
gm : I—L/rp.
'
(6—13)
Since 7'p changes With plate and grid
so
also does g….
.
Values of g… for diñerent commercial triodes range from 200 to 5000
’
micromhos.
‘
?
,
_
The mutual conductance may be measured3 with theci_rcuit
‘
of gure 6—11.
_
The drop across m, of amount AEg ”=_ In sin c_ot
.
_
Eÿ
.
.
’
'
’
_n
—_
% Ep
,
°
‘
‘
—'_
==
—
'.
+
.'
"
‘
,
r3
.
mutual conduètahœ
-
’…
.
_
applied
of thetube
of plate cur—
re‘nfcf amount gmlmsmwttoowthrough ‘thèaPhOæ- This is
‘
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dropIrzsmwmnrzImsassumedtham is
:
—
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