MJ2955 Transistor Data

Key transistor data for the MJ2955 PNP power transistor complementary to 2N3055 including key electrical parameters, pinout, package type and many other key transistor details.

The MJ295555 is a rugged power transistor widely used for amplifier and power switching circuits. It was a popular device used in many power audio amplifiers.

The device is complementary to the 2N3055 enabling class B operation for linear amplifiers.

Both devices are still widely available and manufactured by a variety of manufacturers.

Key details and performance parameters for the MJ2955 transistor.

Transistor parameters & data
Parameters	Details
Transistor type	NPN silicon switching transistor
Package type	TO3
V_CBO max (V)	-100
V_CEO max (V)	-60
V_EBOmax (V)	-7
I_C max (A)	-15
T_J Max °C	200
P_TOT W	115
f_T min (MHz)	2.5
C_OB
h_fe	20 - 70
I_C for h_fe	4 A
Similar / equivalents

Outline:

Pinout:

Explanation of transistor parameters

Parameter	Explanation
V_CBO Max	Maximum collector-base voltage with emitter open circuit .
V_CEO Max	Maximum collector-emitter voltage with base open circuit.
V_EBO Max	Maximum emitter-base voltage with collector open circuit.
V_CEsat (included where applicable)	The voltage drop across the collector-emitter when the transistor is fully saturated (acting as a closed switch).
I_C Max	Maximum collector current.

Parameter	Explanation
T_J	Maximum junction temperature.
P_TOT Max	Maximum device dissipation normally in free air at 25°C unless other conditions indicated.
f_T Min	Minimum cutoff frequency at which the current gain in a common emitter circuit falls to unity.
C_OB Max	Maximum collector capacitane, normally measured with emitter open circuit.
h_FE	DC current gain for H_FE at I_C. [Note hfe is the small signal gain and although this may be slightly different, the transistor current gain will vary considerably from ne transistor to the next of the same type.]
P_TOT Max	Maximum device dissipation normally in free air at 25°C unless other conditions indicated.

These are the main transistor parameers that have been included in our list. There are others, but these help quantify the main elements of the performance of the transistor.

Read more about . . . . Transistor Data-sheet Specifications & Parameters.

Please note, that the data given is the best estimate we can give within a tabulated summary of this nature. Parameters also vary between manufacturers. Electronics Notes cannot accept any responsibility for errors, inaccuracies, etc, although we do endevaour to ensure the data is as accurate as possible.

Notes and supplementary information

This silicon power transistor was for many years the standard PNP power transistor to accompany the 2N3055.

• Mounting the MJ2955

As the collector connection is the case to provide adequate heat-sinking, special insulation kits were available for mounting these power transistors onto a heatsink. A thin mica or similar washer shaped to the outline of the transistor and insulating washers for the screw connections were available.

It was also standard practice to place a small amount of silicon grease on either side of the washer to ensure good thermal contact to the heatsink.

• Availability

The MJ2955 transistor is widely manufactured these days and can be obtained through a number of distributors, although it is classed as obsolete.

The device tends to be manufactured by the second tier manufacturers who have picked up the information from the primary manufacturers who have moved on to more lucrative modern devices.

Not only is it manufactured by some of the mainstream manufacturers, but also a large number of secondary companies as well.

The technology is old, and it is easy to manufacture, and accordingly it is easy for smaller manufacturers to pick the fabrication techniques up.