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CF50

High-gain pentode designed specifically for microphone preamplifiers and other low-level resistance-coupled audio stages.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: P8A
Base pins: 8
Nominal heater: 30 V / 200 mA

Description

High-gain pentode intended for microphone preamplifier and low-level resistance-coupled audio service.

Socket description

European 8-pin side-contact base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: P8A
Base pins: 8
Nominal heater voltage: 30 V
Nominal heater current: 200 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

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: 2500000 Ω
Transconductance: 0.0033 S
Max plate voltage: 250 V
Max plate dissipation: 1 W
Max cathode current: 10 mA

Promoted from clearly identified published ratings/characteristics; additional operating points, capacitances, rectifier conditions, and application-specific values are retained in TUBE_SECTION_PARAMETER.

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

1963 Philips Electron Tubes Handbook V1

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

Plate capacitance
13.8 pF
Section1
Grid capacitance
12.3 pF
Section1
Grid-to-plate capacitance maximum
0.03 pF
Section1

Other

Plate voltage
100 V
MicrophonePreamplifier
Screen voltage
100 V
MicrophonePreamplifier
Control-grid voltage
-2 V
MicrophonePreamplifier
Plate current
1.5 mA
MicrophonePreamplifier
Screen current
0.3 mA
MicrophonePreamplifier
Application
Microphone preamplifier
Section1

Characteristic

Transconductance
3300 µS
Section1
Amplification factor
45
Section1
Plate resistance
2.5 MΩ
250VPlate

Data set 02

1999 Philips 0-D

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

Typical plate voltage
250 V
Maximum screen dissipation
0.5 W