FDD20

Small Signal Triode — P8A

Lorenz/SEL

Known Equivalents & Substitutes

No known equivalents. If you know of any, use the ⚑ Report Issue button above.

Similar Tubes (Not Drop-In Compatible)

Same electricals but UX6 base and 6.3V heater

6N7G

Same electricals but Octal base and 6.3V heater — FDD20 uses P8A base and 13V heater

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)330V

Anode Dissipation (max)Anode Dissipation (max, Class A per section)1.1W

Cathode Current (max)Peak Plate Current (max, Class B per section)140mA

Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)100V

Max Grid ResistorMax Grid Resistor (Class A, self-bias)0.5MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage250V

Grid 1 Bias VoltageGrid Bias Voltage-5V

Anode CurrentAnode Current (per section)35mA

Anode ResistanceAnode Resistance11,000Ω

TransconductanceTransconductance

Heater

Heater VoltageHeater Voltage13V

Heater CurrentHeater Current0.35A

Notes

Both triode sections share a common cathode — separate cathode biasing per section is not possible.
With exception of heater ratings and base, this tube is very similar to 6A6 and 6N7G (per Taschenbuch zum Röhren-Codex 1948/49).
Parameters are derived from the 6N7 GE datasheet, as no dedicated FDD20 manufacturer datasheet could be located. The 6N7 has identical electrical characteristics per the Röhren-Codex.
Class A Pa_max is only 1.0 W per section; Class B Pa_max is 5.5 W per section. The tube is primarily intended for Class B push-pull service or Class A driver use.
Also manufactured by Philips Italy (Milano) per radiomuseum.org.
13V heater is typical of European series-heater designs for AC/DC (transformerless) receivers.

Socket-Compatible Tubes ⚠ Not electrically compatible

References

3.2mA/V

Amplification Factor (μ)Amplification Factor (μ)35—