DF 21
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BrandPhilips
ClassPentode
BaseLoctal
Construction
Primary TypeHF Pentode
EnvelopeGlass
SectionsSingle
Filament / Heater
MaterialDirectly Heated
Absolute Maximum Ratings
Plate Voltage135 V
Plate Dissipation0.2 W
Grid 2 Voltage135 V
Grid 1 Voltage-0.2 V
Cathode Current2.5 mA
Audio Performance
Typical THD0.75%
Key Features
- Low filament current (25 mA)
- Suitable for H.F., M.F. and L.F. amplification
- Directly heated
- Parallel or series filament supply
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| H.F. / M.F. Amplifier | 90V | 700 | 2000000 | 30 | 1.2mA |
| L.F. Amplifier | 120V | - | 1000000 | 85 | 0.28mA |
Application Notes
The DF 21 is a battery pentode designed for low current consumption. It can be used in H.F. and M.F. stages with AGC, or as an L.F. resistance-coupled amplifier where it can achieve a gain of up to 85.
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