120
6.
HIGH VACUUM, LOW—VOLTAGE TUBES
"
*
g
‘
172 sin wt occurring across 72. A small compensation for the grid—_ _‘
plate capacity of the triode is made by means of the condenser C'.
_
After adjusting 72 and C until there is no sound in the phones,
,u]n sin wt = 172 sin col,
(6—4)
_
-
,u = r2/71.
(6—5)
Values of ,a Will be found to be essentially constant for a given tube
over considerable ranges of grid, lament and plate voltages.
;
E E
It is convenient ‘to imagine a triode re.
_
9
?
placed by an equivalent diode. The coml
2
3
.
.
»
,
A
b1ned effect of the plate and grid charges
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.
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-
‘
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upon the space charge is to be replaced by“
'
.
that of a single anode. Thus, in gure 6—7,
B
A represents the triode and B its equivalent
‘_
"’
diode.
The plate (4) of the diode is to have
'
E4
a
suitable potential E; such as Will replace
F
6 7
d' d
B
the total effects of the grid potential E,;
1G—
"
.
10
€
.
.
equivalent to a… ode A.
and the plate potential E,, of the tr10de.
We may consrder the electrodes as the
of condensers.
charges per
unit area in the two cases must
be equal, so that
‘
C14E; = C12Ea + 013Ep,
(6—Ô)f
where the C’s are the capacity coefcients for the electrodes, cor_
,
responding to their subscripts. Inasmuch as 014 is nearly equal
to Clg in actual tubes, we may write '
,
-
‘
‘
El
Eg + _ Ep(6—7)
Thusthe lumpàd voltage E; of the equivalent diode is
'
1Ythat0f'the grid of the triode plus a fraction of that of theplat
":
__
Thlsfractlon, C713/
called the penetration faàtor and is” custom—
D.*
“Its recipr0Cal is thevoltag@
amplicaü@nœnstantu Then, — -
=
,
+
'
El: E: “l‘—2
»
'Ï ‘
l
*DurchgnfïmGerman
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