PL8877/
3CX1500A7
High-Mu
Power Triode
The Penta Laboratories PL8877/3CX1500A7 is a rugged ceramic and metal power triode designed for
use as cathode driven Class AB2 or Class B amplifi er in audio or rf applications including the VHF band,
or as a cathode driven plate modulated Class C rf amplifi er. As a linear amplifi er, high power gain may be
obtained without sacrifi ce of low intermodulation distortion characteristics.
Low grid interception and high amplifi cation factor combine to make the PL8877/3CX1500A7 drive power
requirements exceptionally low for a tube of this power capacity.
General Characteristics
Electrical
Cathode ..............................................................................Oxide Coated, Unipotential
Cathode Heater
Voltage .....................................................................................................5.0 ± 0.25 Volts
Current (Ef = 5.0 Volts) .....................................................................................10.5 Amperes
Transconductance (Ib = 1.0 Adc) ........................................................................ 55,000 μmhos
Amplifi cation Factor (average)................................................................................. 200
Direct Interelectrode Capacitance (Grounded Filament)
Cin .................................................................................................................... 38.5 pF
Cout .................................................................................................................... 0.1 pF
Cpg ...................................................................................................................... 10 pF
Direct Interelectrode Capacitance (Grounded Grid)
Cin .................................................................................................................... 38.5 pF
Cout ..................................................................................................................... 10 pF
Cpg ..................................................................................................................... 0.1 pF
Ck-htr ..................................................................................................................9.7 pF
Frequency of Maximum Operation (CW) ................................................................. 250 MHz
1. Characteristics and operating values are based upon performance tests. These fi gures may change
without notice as a result of additional data or product refi nement.
2. Capacitance values are for a cold tube as measured in a special shielded fi xture.
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Revised 18 January 2022
P E N T A L A B O R A T O R I E S
14399 PRINCETON AVENUE * MOORPARK * CALIFORNIA 93021
(800) 421-4219 * (818) 882-3872 * FAX: (818) 882-3968
ELECTRON TUBES FOR INDUSTRY
PL8877/3CX1500A7 High-Mu Power Triode
Mechanical
Maximum Overall Dimensions
Length ............................................................................................................... 4.02 Inch
Diameter ........................................................................................................... 3.38 Inch
Net Weight ................................................................................................................. 25 Ounces
Operating Position ...................................................................................................Any
Maximum Operating Temperatures
Ceramic/Metal Seals ........................................................................................250° C
Anode Core ......................................................................................................250° C
Cooling ......................................................................................................... Forced-Air
Base ......................................................................................................... Special 7-pin
Recommended Air Socket System
Grounded Cathode ..................................................................................PSK-2200
Grounded Grid .........................................................................................PSK-2210
Recommended Air Chimney ..........................................................................PSK-2216
Range Values For Equipment Design
Min. Max.
Heater Current (Ef = 5.0 Volts) ..................................................................... 9.5 11.5 Amperes
Cathode Warm-up Time .............................................................................. 180 --- Seconds
Interelectrode Capacitance
Input ...................................................................................................... 36.0 41.0 pF
Output ..................................................................................................... 9.2 11.2 pF
Feedback ..................................................................................................--- 0.2 pF
1
(Grounded Grid Circuit)
1. In shielded fi xture.
Maximum Ratings and Typical Operating Conditions
Radio Frequency Linear Amplifi er Cathode Driven Class AB
Absolute Maximum Ratings
DC Plate Voltage ................................................................................................... 4000 Volts
DC Plate Current ...................................................................................................... 1.0 Amperes
Plate Dissipation .................................................................................................... 1500 Watts
Grid Dissipation ......................................................................................................... 20 Watts
Typical Operation
(Frequencies to 30 MHz) Class AB2 Cathode Driven
Peak Envelope or Modulation Crest Conditions
Plate Voltage ............................................................................................. 2700 3500 Vdc
1
Cathode Voltage
Zero-Signal Plate Current
....................................................................................... +8.2 +8.2 Vdc
3
............................................................................ 92 182 mAdc
Single-Tone Plate Current ........................................................................... 740 1000 mA
Two-Tone Plate Current ............................................................................... 480 675 mA
Single-Tone Grid Current
3
............................................................................. 40 74 mAdc
Two-Tone Grid Current3 ................................................................................. 16 25 mAdc
3
Peak rf Cathode Voltage
Peak Driving Power
.............................................................................. 68 81 Volts
3
..................................................................................... 40 64 Watts
Driving Impedance......................................................................................... 58 51 Ohms
Single-Tone Useful Output Power3 ............................................................ 1085 2075 Watts
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2
PL8877/3CX1500A7 High-Mu Power Triode
Resonant Load Impedance ....................................................................... 1820 2000 Ohms
Intermodulation Distortion Products
2
3rd Order ................................................................................................ -40 -38 dB
5th Order ................................................................................................-41 -41 dB
1. Positive cathode bias provided by zener diodes.
2. The intermodulation distortion products are referenced against one tone of a two equal tone signal.
3. Approximate values.
Typical Operation
(200 MHz) Class AB2 Cathode Driven
Plate Voltage ......................................................................................................... 2500 Volts
1
Cathode Voltage
...................................................................................................+8.2 Volts
Plate Current ......................................................................................................... 1000 mAdc
Grid Current2 ............................................................................................................. 10 mAdc
Useful Output Power2 ............................................................................................1520 Watts
Driving Power2 ........................................................................................................... 57 Watts
Power Gain2 .............................................................................................................. 14 dB
Radio Frequency Power Amplifi er
Class B Telegraphy or FM (Continuous Operating Conditions)
Absolute Maximum Ratings
DC Plate Voltage ................................................................................................... 4000 Volts
DC Plate Current ...................................................................................................... 1.0 Ampere
Plate Dissipation .................................................................................................... 1500 Watts
Grid Dissipation ......................................................................................................... 20 Watts
Typical Operation (88-108 MHz)
Measured Values Class B, Cathode Driven
Plate Voltage ......................................................................2000 2500 3000 4000 Vdc
1, 2
Cathode Voltage
.................................................................+9 +12 +15 +20 Vdc
Plate Current .........................................................................1.0 1.0 1.0 1.0 Adc
Grid Current2 ..........................................................................60 58 42 25 mAdc
Driving Power2 ........................................................................64 54 65 78 Watts
Useful Output Power3 .........................................................1330 1670 1960 2600 Watts
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Effi ciency
Power Gain
............................................................................66.5 66.7 65.5 65.2 %
4
........................................................................13.2 14.2 14.8 15.3 dB
1. For measured case, idling anode current was set to 10 mAdc.
2. Approximate.
3. Approximate, delivered to load.
4. For the measured case, may vary from tube to tube.
Radio Frequency Power Amplifi er
Class C - Cathode Driven, Plate Modulated
Absolute Maximum Ratings
DC Plate Voltage ................................................................................................... 3200 Volts
DC Plate Current ...................................................................................................... 0.8 Amperes
Plate Dissipation .................................................................................................... 1000 Watts
Grid Dissipation ......................................................................................................... 20 Watts
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