3A5

3A5 is also designated DCC90.

The 3A5 is a dual triode tube containing two triode units with a directly heated coated filament.

Construction

The tube uses a T-5 1/2 bulb and a miniature button 7-pin base. Its maximum overall length is 2-1/8 inches, maximum seated height is 1-7/8 inches, and maximum diameter is 3/4 inch. The filament can be operated in series or in parallel. For parallel operation, the filament voltage is 1.4 volts at 220 milliamperes; for series operation, the filament voltage is 2.8 volts at 110 milliamperes.

Capacitance

The RCA datasheet gives the direct interelectrode capacitance values for each triode unit as follows: grid to filament, 0.9 picofarads; plate to filament, 1.0 picofarad; grid to plate, 3.2 picofarads. Between the two triode units, the direct capacitance is 0.22 picofarad between plates and 0.9 picofarad between grids.

Characteristics

At a plate voltage of 90 volts and a grid voltage of −2.5 volts, each triode unit has an amplification factor of 15, a plate resistance of 8300 ohms, a transconductance of 1800 micromhos, and a plate current of 3.7 milliamperes. The Mullard datasheet gives the same typical characteristics for each triode at these operating conditions.

Ratings

For class C telegraph service, the RCA datasheet gives maximum ratings of 135 volts plate voltage, −30 volts grid voltage, 15 milliamperes plate current per unit, 2.5 milliamperes grid current per unit, 1.0 watt plate dissipation per unit, and 2.0 watts plate input per unit. For audio-frequency power amplifier service, the RCA datasheet gives maximum ratings of 135 volts plate voltage, 5 milliamperes plate current, and 0.5 watt plate dissipation. The Mullard datasheet lists maximum anode voltage as 135 volts, maximum grid voltage as −30 volts, maximum anode current as 2×15 milliamperes, maximum grid current as 2×2.5 milliamperes, and maximum anode dissipation as 2×1 watt for intermittent operation; for continuous operation, these limiting values must be reduced by 50 percent.

Typical Operation

The RCA datasheet gives typical operation as a push-pull radio-frequency power amplifier or oscillator at 40 Mc with both units in push-pull at a plate voltage of 135 volts. In this service, the typical plate current is 30 milliamperes, grid current approximately 5 milliamperes, driving power approximately 0.2 watt, and power output approximately 2 watts.

Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.

Original manufacturer datasheets for 3A5, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• 3.75
• DCC90 (filed under DCC90)

1 further designation appears alongside 3A5 in the literature but below the evidence threshold used here, so it is not listed as equivalent.