DF21

Low-filament-current battery pentode designed for RF, IF, and audio-frequency amplification in portable receiving equipment.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: IO
Base pins: 8
Nominal heater: 1.4 V / 25 mA

Description

Low-filament-current R.F., I.F. and A.F. battery pentode. The supplied Philips sheet was read for heater/filament data, ratings, characteristics, capacitances, and operating conditions where published.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: IO
Base pins: 8
Nominal heater voltage: 1.4 V
Nominal heater current: 25 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: Yes

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 3000000 Ω
Transconductance: 0.00082 S
Max plate voltage: 135 V
Max screen voltage: 135 V
Max plate dissipation: 0.2 W
Max screen dissipation: 0.1 W
Max cathode current: 2.6 mA

Principal RF/IF characteristic at 90 V promoted.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1999 Philips 0-D

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

Anode-grid capacitance maximum
0.008 pF
Control-grid capacitance
5.3 pF

Characteristics

Plate voltage
90 V
RF/IF
Screen voltage
90 V
RF/IF
Grid bias
-0.5 V
Uncontrolled
Plate current
0.85 mA
Screen current
0.18 mA
Transconductance
820 uS
Plate resistance
3 Mohm

Other

Voltage gain
85
AF;BatteryVoltage=120V;Ra=0.5Mohm