Page 1
Page 2
300B Vacuum Tube
Classication
Moderate power, lamentary triodes for
Class A service
Application
Audio-frequency amplier in positions
where power outputs of approximately
ten watts or less are required at
relatively low plate voltages.
Dimensions
Dimensions, outline diagrams of the
tubes and bases, and the arrangement
of electrode connections to the base
terminals are shown in Figures 1 and 2.
Base and Mounting
These vacuum tubes employ medium,
four-pin thrust type bases suitable for
use in Western Electric 143B or similar
sockets. The 300B tube has the bayonet pin so located that it may also be
mounted in a Western Electric 100M,
115B or similar socket.
The tubes may be mounted in either a
vertical or horizontal position. If mounted in a horizontal position, the plane
of the lament, which is indicated in
Figure 2, should be vertical.
Average Direct Interelectrode
Capacitances
Grid to plate ............................. 15 �� f.
Grid to lament .......................... 9 �� f.
Plate to lament ...................... 4.3 �� f.
Filament Rating
Filament voltage ...5.0 volts, a.c. or d.c.
Nominal lament current ... 1.2 amperes
The laments of these tubes are
designed to operate on a voltage basis
and should be operated at as near the
rated voltage as possible. When alternating current is used for heating the lament,the grid and plate returns should
be connected to a center tap on the
secondary of the lament transformer.
Characteristics
Average characteristics -
(Ef = 5.0 volts, a.c., Eb = 300 volts
and Ec =—61 volts).
Plate current ................60 milliamperes
Amplication factor ........................3.85
Plate resistance .................... 700 ohms
Grid to plate
transconductance .......5500 micromhos
Limiting Operating Conditions
for Safe Operation
Not simultaneous ratings
Maximum plate voltage ...........450 volts
Maximum plate dissipation ......40 watts
Maximum plate current of average tube
for xed grid bias .........70 milliamperes
Maximum plate current for manually
adjusted grid bias or self-biasing
circuit. ........................100 milliamperes
Recommended Operating Conditions
Recommended and maximum conditions for alternating-current lament
supply 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 operating conditions will
be shorter than at the recommended
conditions.
Where it is necessary to operate the
tube at or near the maximum plate
current of 100 milliamperes, provision
should be made for adjusting the grid
bias of each tube independently, so that
the maximum safe plate current will not
be exceeded in any tube. Alternatively,
a self-biasing circuit may be used, in
which the grid bias for the tube is obtained from the voltage drop produced
by the plate current of that tube owing
through a resistance.
Where it is necessary to use a xed
grid bias, the plate current of the
average tube should be limited to a
maximum value of 70 milliamperes, so
that tubes having plate currents higher
than the average will not exceed the
maximum safe plate current.
Page 3
300B Vacuum Tube
Power Output and Distortion
Performance data including power output, second and third harmonic levels
for a number of operating conditions
are given in the table.
The variation of power output and
harmonic levels with load resistance
for several values of operating plate
current are shown in Figures 7, 8 and
9, for a plate voltage of 350 volts.
Grid
Bias
Plate
Current
Plate
Voltage
Volts Volts Milliamps Ohms Watts db db
200 -42 30 2000 3.0 20 31
200 -39 40 2500 2.6 26 38
200 -37 50 2500 2.5 30 45
250 -55 30 2000 4.9 18 27
250 -55 30 4500 3.2 27 40
250 -52 40 3000 4.0 26 36
250 -50 50 2500 4.4 26 39
250 -48 60 2000 4.7 26 38
250 -48 60 2700 4.1 30 45
250 -45 80 1500 5.0 26 41
300 -65 40 2500 6.7 20 30
300 -63 50 2000 7.2 21 29
300 -63 50 3000 6.1 26 37
300 -61 60 2400 6.6 26 37
300 -61 60 3400 5.6 30 44
300 -58 80 1700 7.5 26 37
350 -76 50 3600 7.8 26 38
350 -76 50 5000 6.2 30 45
350 -74 60 2000 10.2 21 30
350 -74 60 3000 8.3 26 38
350 -74 60 4000 7.0 30 44
350 -71 80 2200 9.6 26 39
400 -91 40 5000 8.4 26 37
400 -89 50 3000 11.5 21 31
400 -89 50 4000 9.4 25 38
400 -87 60 3500 10.5 26 38
400 -87 60 5000 8.3 30 46
400 -84 80 2500 12.5 25 37
450 -104 40 6000 9.5 26 38
450 -102 50 5000 10.7 27 39
450 -102 50 6500 9.0 30 45
450 -100 60 4000 12.5 26 38
450 -100 60 5500 10.1 30 44
450 -97 80 2000 17.8 21 30
450 -97 80 3000 14.6 26 37
450 -97 80 4500 11.5 31 45
Load
Resistance
Power
Output
2nd
Harmonic
The peak value of the sinusoidal
input voltage, Egm, which gives the
indicated power output, Pm and
harmonic levels, F2m and F3m for
each point in both the curves and
the table, is numerically equal to the
grid biasing voltage at that point.
For a smaller input voltage Eg, the
approximate levels may be computed
from the following relations.
3rd
Harmonic
14
12
10
8
IN WATTS
6
FUNDAMENTAL POWER OUTPUT
4
2
0
10
20
30
40
SECOND HARMONIC IN DB
BELOW THE FUNDAMENTAL
50
0
20
30
60
50
THIRD HARMONIC IN DB
60
BELOW THE FUNDAMENTAL
70
0
4
1
3
1000
2000
1000
2000
1000 3000 7000 8000 9000 10000 11000 1200050002000 4000 6000
2
P = Pm
Eg
(
Egm
)
Eg
F2 = F2m+20 log10
Egm
Eg
F3 = F
FILAMENT VOLTAGE = 5.0 VOLTS A.C.
PLATE VOLTAGE = 350 VOLTS
INPUT IN PEAK VOLTS = GRID BIAS
2
3000
3000
CURVE PLATE GRID
CURRENT BIAS
1 30 -81
2 40 -78
3 60 -74
4 80 -71
4
6000
6000
7000
1
2
3
4
7000
1
2
3
4
5000
4000
4000
LOAD RESISTANCE IN OHMS
FIG. 7
5000
FIG. 8
FIG. 9
3
8000
8000
+ 40 log
3m
1
2
9000
9000
10000
10000
10
Egm
11000
11000
12000
12000
Page 4
300B Vacuum Tube
Characteristics
Plate-current characteristics for a
typical tube are shown in Figure
3 as functions of grid bias, for
alternating-current lament supply.
The corresponding amplication-factor,
plate-resistance, and transconductance
characteristics are given in Figures
4, 5 and 6, respectively. When directcurrent lament supply is used, and the
grid and plate returns are connected
to the negative end of the lament, the
same characteristics are applicable if
3.5 is subtracted from the numerical
value of each grid bias.
4.2
FILAMENT VOLTAGE = 5.0 VOLTS A.C.
4.0
3.8
3.6
AMPLIFICATION FACTORTRANSCONDUCTANCE
-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
Eb = 450
400
350 300 250 200 150 100
FIG. 4
1600
1400
1200
Eb = 450
1000
800
PLATE RESISTANCE IN OHMS
600
400
-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
400 350 300 250 200 150 100
FIG. 5
8000
7000
6000
5000
4000
3000
2000
1000
-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
Eb = 450
90
80
70
60
50
40
400 350 300 250 200 150 100
GRID VOLTAGE
FIG. 6
FILAMENT VOLTAGE =
5.0 VOLTS A.C.
Eb = 450 400 350 300 250 200 150 100
30
20
PLATE CURRENT IN MILLIAMPERS
10
0
-120-130 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
GRID VOLTAGE
FIG. 3
Page 5
300B Vacuum Tube
Ordering Information
(Order by Code and Comcode)
Electron Tubes
Code Application Comcode
300B Moderate Power Triode 100792522
Western Electric™ High Fidelity products are marked worldwide
Exclusively by Western Electric™
Western ElectricTM Electron tubes are manufactured in the U.S.A. developments of Bell
Telephone Laboratories.
For more information please contact a
Western Electric™ Sales Representative.
Western Electric™
410 Chickamauga Avenue, Suite 300
Rossville, GA
Phone: 404-352-2000
www.westernelectric.com
Western ElectricTM reserves the right to make changes to
the product(s) described in this document in the interest
of improving internal design, operational function and/or
reliability. Western Electric
occur due to use or application of the product(s) or the circuit
layouts described herein.
Copyright © 2016 Western Electric
All Rights Reserved. Printed in the U.S.A.
TM
assumes no liability which may
TM
Export Corporation.
Page 6
Western Electric Export Corporation
410 Chickamauga Avenue, Suite 300
Rossville, Georgia 30741
Phone: 404-352-2000
www.westernelectric.com
Western ElectricTM is a trademark of Western ElectricTM Export Corporation.
Copyright © 2016 Western Electric Export Corporation.
All Rights Reserved. Printed in the U.S.A. • Rev. 8/16
TM
Loading...