Western electric 352 a brochure

Page 1

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352A Vacuum Tube

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Classification-Duodiode triode with an indirectly heated cathode

The 352A tube comprises three distinct vacuum tube units which are independent of each
other except that sections of a single cathode structure supply electron emission for all three. Two
of these units are diodes. The other is a triode.

Applications-Diode detector, diode rectifier for automatic volume control voltage, and triode
audi0~frequency amplifier. if desired the two diodes may be used for full-wave rectification or they
may be connected in parallel to provide a lower impedance half-wave rectifier. The former con-
nection requires about twice as high an input voltage as the latter to give equal detector output.

Dimensions and Connections-Outline diagrams of the tube and base giving the dimensions
and the arrangement of the electrode connections to the base terminals are shown in Figures 1 and 2.

Base and Mounting-This tube employs a small six-pin thrust type base suitable for use in a
Western Electric 1443 or similar socket. The base pins are silver plated. The triode grid terminal
is a small metal cap located at the top of the bulb.

This tube may be mounted in any position.

Copyright 1939 Western Electric Company, Incorporated

Page 2

Average Direct Interelectrode Capacitances

Triode grid to plate ................ . . ...... 1.5 puf
Triode grid to cathode and heater ....... . . 1.6 ##f
Triode plate to cathode and heater. ........ . . . . . 3.8 uuf
Both diodes to triode grid ................. . . . , . . . . . . 0.015 ##f
Both diodes to triode plate. . . . ..................... 1.4 of
Both diodes to cathode and heater ..... . . ............. 6.5 puf
Heater Rating

Heater voltage . . .............. . . ...... . . 10.0 volts, a.c. or do.
Nominal heater current. . . . . . . . . . . . . . ...... 0.32 ampere

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

Cathode Connection-Where alternating heater voltage is used the cathode should pref-
erably be connected directly to the mid-point of the heater transformer winding or to the mid-
point of a low resistance connected across the heater terminals. For direct current operation the
cathode may be connected to either end of the heater. If voltage is applied between the heater
and cathode, it should be kept low and must not exceed 50 volts.

Triode Characteristics-Typical curves showing triode plate current as a function of grid
voltage for several values of plate voltage are shown in Figure 3. Corresponding amplification
factor, plate resistance and transconductance characteristics are given in Figures 4, 5 and 6 re-
spectively. Figure 7 shows plate current as a function of plate voltage for several values of grid
voltage.

Trlode Operating Conditions and Output

Permissible operating plate and grid voltages are included within the area, ABCD, in Figure 3.
Amplification factor, plate resistance. transconduetance and performance data for a number of
typical operating conditions are given in the table. Recommended conditions or others of no
greater severity should be selected in preference to maximum conditions wherever possible. The
life of the tube at maximum opeeating conditions will be shorter than at less severe conditions.

In the last four columns of the table are given the fundamental power output, Pm, in milliwatts,
the fundamental voltage output, Em. in peak volts and the second and third harmonic levels, FM
and Firm in db below the fundamental, for the indicated values of load resistance. The peak
value of the sinusoidal input voltage, Em, is numerically equal to the grid bias in each case.
here the level of the third harmonic is lower than 45 db below the fundamental, its value may
be widely different from tube to tube. The values given represent a typical tube.

For a smaller input voltage, EH, the fundamental power and voltage outputs and the harmonic
levels are given approximately by the following relations:

E -Em#
P P Egm
F -FZm-:-Zolog E
2 HIOEg
E
F3 =F3m+4olongim
E