Since 1872   
WE 274B
Western Electric™ 274B Vacuum Tube
Classification: Full-wave, Thermionic High Vacuum Rectifier.

Application: The 274B tube is designed to supply direct current up to 200 milliamperes from an alternating current source. It comprises two filament type diode units with a common filament.

Dimensions
Dimensions, outline diagrams of the tube and base, and the arrangement of electrode connections to the base terminals are shown in Figures 1 and 2.

Base
Medium, octal five pin type.

Socket
Standard octal five pin type such as the WE B5-15.

Mounting Positions
Either vertical or horizontal. If mounted in a horizontal position, the planes of the filament, whose direction is indicated in Figure 2, should be vertical.

Filament Rating
Filament voltage: 5.0 volts, a.c. or d.c.

Nominal filament current: 2.0 amperes

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

Effect of Filter
It is evident from the regulation characteristics of Figures 4 and 5 that for a given output current and voltage, the choke-input filter requires a somewhat higher alternating voltage applied to the plates of the tube than the capacitor-input filter. With the capacitor input filter, however, the normal charging and discharging of the capacitor each half cycle requires the tube to supply relatively large peaks of current during each charging period. The peak current increases in value as the capacitance of the capacitor is increased and may be much larger than the average rectified output current, though its duration in such cases is only a short fraction of a cycle. Since for good tube performance, the anode current must be considerably less at every part of the cycle than the total emission current from the filament, the maximum permissible output current must be limited to such a value that this condition is satisfied. The permissible output current may be larger, therefore, for a choke-input filter, in which the peak anode current is only slightly larger than the output current. The choke-input filter also gives much better regulation than the capacitor-input circuit. The choke-input filter, therefore, should always be selected in preference to the capacitor-input filter wherever possible. With a capacitor-input filter, the capacitance of the input capacitor should preferably not exceed 4 microfarads.

Characteristics
The current-voltage characteristic of a single diode unit of the 274B tube is shown in Figure 3. The voltage is measured between the plate and a center tap on the filament transformer. Direct-voltage output characteristics as functions of the direct load current for a number of values of applied alternating voltage are given in Figures 4 and 5. The characteristics of Figure 4 are for a choke-input filter such as is shown in circuit A, and those of Figure 5 are for a capacitor-input filter such as is shown in circuit B.

Filament Voltage...............................................5.0 volts
Maximum Plate Voltage (RMS) per Plate............660 volts
Maximum D-C Output Current.............................225 ma

General Characteristics

Electrical Data
Filament Voltage...........................5.0 volts
Filament Current..........................2.0 amps

MECHANICAL DATA

Cathode ...........................Coated filament
Bulb..................................................ST16
Base..........................Medium 5-pin, octal
Mounting Position.........Preferably vertical; if horizontal, pins #1 and 4 should be in vertical plane.

Maximum Ratings

Design-Center Values
Peak Inverse Voltage .................................................1500 volts
Peak Plate Current per Plate...........................................675 ma
Peak Transient Plate Current per Plate.........................2.5 amps

With Choke-Input Filter:
A-C Plate Voltage per Plate (RMS)............................660 volts
D-C Output Current .....................................................225 ma
Minimum Input-Choke Inductance.............................3 henrys

With Capacitor-Input Filter:
A-C Plate Voltage per Plate (RMS)...........................450 volts
D-C Output Current......................................................160 ma
Min. Total Eff. Plate-Supply Impedance per Plate....100 ohms


Ordering Information:

Code 274B Electron Tube
Application Full Wave Rectifier
Comcode 100792399
 
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