Western electric 231 d brochure

Page 1

BELL SYSTEM PRACTICES SECTION AB46.170
Transmission Engineering and Data Issue 1, September 1936
Vacuum Tube Data A T & 1 Co Standard

Wafer/7 Elect/12
231D Vacuum Tube

Classification-Small, filamentary triode

An important feature of the 231D tube is its low filament power consumption

Applications
Audio-frequency and intermediate-frequency amplifier.
Detector.

Oscillator.

Dimensions-Outline diagrams showing dimensions of the tube and base, and the arrangement
of the electrode connections to the base terminals are given in Figures 1 and 2.

Base-Small, four-pin, thrust type.
Socket-Standard four-contact type such as the Western Electric 143B socket.

Mounting Positions-Either vertical or horizontal. If mounted in a horizontal position the
plane of the filament, which is indicated in Figure 2, should be vertical.

Copyright 1936, Western Electric Company, Incorporated

231 I)

Page 2

231D

Average Direct Interelectrode Capacitances

Grid to plate ...... 3 6 ant.
Gridtofilament.............. 25pyf
Plate to filament ....................................... 2.5 ppf.

Filament Rating

0.060 ampere, d.c.
3.1 volts

Filament current. . . . ....... .
Nominal filament voltage ,,,,,,

The filament of this tube is designed to operate on a current basis and should be operated at as
near the rated current as is practicable.

Characteristics-Plate current characteristics of a typical 231D tube are shown in Figure 3 as
functions of grid voltage for several values of plate voltage. The grid and plate voltages are mea-
sured from the negative end of the filament. Corresponding amplification factor, plate resistance,
and transconductance characteristics are given in Figures 4, 5 and 6, respectively. Plate current
characteristics as functions of plate voltage are shown in Figure 7 for several values of grid voltage.

Operating Conditions and Output-Permissible operating plate and grid voltages are in-
cluded within the area, ABCD, in Figure 3. Amplification factor, plate resistance, transeonductance,
and performance data are given in the table on page 3 for a number of typical operating conditions
represented by selected points within this area. The less severe operating conditions should be
selected in preference to maximum operating conditions wherever possible. The life of the tube
at maximum conditions may be shorter than at less severe conditions.

The performance data include the fundamental power or voltage output and the second and
third harmonic levels {or the indicated values of load resistance. The fundamental output is given
in terms of the power, Pm, in milliwatts for values of load resistance, R, equal to and double the
value of the plate resistance. r;., and in terms of the voltage, Em, in peak volts for values of load
resistance five times the plate resistance. The second and third harmonic levels, Fgm and Fgm,
are given in decibels below the fundamental in each case The peak value of the sinusoidal input
voltage, Em, is numerically equal to the grid bias for each operating condition. For a smaller input
voltage, E5, the fundamental power and voltage output and the harmonic levels are given approxi-
mately by the following relations:

F2 = 1:211: + 20 logic E-gm
3

F3: F3m + 4010g10 %

z

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