Skip to main content
Tube Tinker — Electron Tube Database
Alternatives & variationsDownload PDF datasheet

Voltage Pentode ·Pentode

7721

High-transconductance long-life pentode for wide-band amplification, explicitly paired with D3A in manufacturer literature. It combines substantial gain-bandwidth capability with extended service life for professional broadband signal equipment.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
9EQ
Socket code
B9A
Base pins
9
Nominal heater
6.3 V / 320 mA

Description

The Telefunken 7721 is a high-transconductance long-life pentode for wide-band amplification, with the sheet explicitly pairing D3A and 7721.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
9EQ
Socket code
B9A
Base pins
9
Nominal heater voltage
6.3 V
Nominal heater current
320 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

9EQ - Terminal pinout

Electrical assignments shared by every tube using this base designation.

TerminalSectionConnectionEvidence
PIN1Base Pin—K — Cathode

Original chart label: K; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN2Base Pin—G1 — Control Grid

Original chart label: G1; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN3Base Pin—K — Cathode

Original chart label: K; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN4Base Pin—H — Heater

Original chart label: H; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN5Base Pin—H — Heater

Original chart label: H; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN6Base Pin—IC

Original chart label: IC; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN7Base Pin—P — Plate (Anode)

Original chart label: P; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN8Base Pin—G3 — Suppressor GridGroup 9EQ8

Original chart label: G3; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN8Base Pin—IS — Internal ScreenGroup 9EQ8

Original chart label: IS; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

PIN9Base Pin—G2 — Screen Grid

Original chart label: G2; manufacturer verification pending

Unverified

EIA Base Connections, printed page 132, 9EQ

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
120000 Ω
Transconductance
0.035 S
Max plate voltage
220 V
Max screen voltage
180 V
Max plate dissipation
4.2 W
Max screen dissipation
1 W
Max cathode current
30 mA
Rectifier warm-up time
60 s

Published maximum ratings and characteristic constants promoted; identical twin sections compressed when applicable.

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

1959 Telefunken

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

  • Plate Supply Voltage

    190 V

  • Screen Supply Voltage

    160 V

  • Plate Current

    24 mA

  • Transconductance

    35000 uS

  • Plate Resistance

    120000 ohm

  • Guaranteed Life

    10000 h

    Average of 100 tubes

  • Noise Figure

    7 dB

    100MHz

  • Approximate Gain-Bandwidth Figure

    230 MHz

Data set 02

1960 CBS Hytron

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • Input capacitance

    10 pF

  • Output capacitance

    2 pF

  • Grid-to-plate capacitance

    0.035 pF

Other

  • Peak plate voltage

    400 V

    IntermittentOperation

  • Peak screen-grid voltage

    400 V

    IntermittentOperation

  • Plate supply voltage

    190 V

    ClassA

  • Screen-grid supply voltage

    160 V

    ClassA

Characteristics

  • Plate current

    22 mA

  • Screen-grid current

    6 mA

  • Equivalent noise resistance

    50 Ohm

Data set 03

1963 Siemens

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Heater voltage

    6.3 V

  • Heater current

    345 mA

Characteristics

  • Transconductance

    35000 µS

    Nominal/Bogey

Data set 04

1965 Ericsson Longlife

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • Input capacitance

    10 pF

  • Output capacitance

    2 pF

  • Grid-to-plate capacitance

    0.035 pF

Other

  • Peak plate voltage

    400 V

    IntermittentOperation

  • Peak screen-grid voltage

    400 V

    IntermittentOperation

  • Plate supply voltage

    190 V

    ClassA

  • Screen-grid supply voltage

    160 V

    ClassA

  • Transconductance minimum

    30000 uS

  • Transconductance maximum

    40000 uS

Characteristics

  • Plate current

    22 mA

  • Screen-grid current

    6 mA

  • Transconductance

    35000 uS

  • Plate resistance

    0.12 MOhm

  • Equivalent noise resistance

    150 Ohm

Data set 05

196X LM Ericsson

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

  • Heater voltage

    6.3 V

  • Heater current

    320 mA

  • Plate resistance

    150 ohm

  • Transconductance

    50000 uS

  • Amplification factor

    2

  • Application

    Broadband low-noise beam pentode

Other

  • Maximum plate voltage

    400 V

  • Maximum screen voltage

    400 V

  • Maximum plate dissipation

    4.5 W

  • Heater-cathode voltage

    60 V