- slide 1 of 6
The 2N3055 is a NPN Epitaxial-Base Planar Transistor that normally comes encapsulated in a metal Jedec TO-3 package. The basic application range include power switching, high fidelity amplification, shunt regulation, and forming the output stages of various power circuits.
The device has become particularly popular due to some of its outstanding features, as summarized below:
- Rugged design and packaging, makes it less vulnerable to mechanical stresses during procurement and transportation.
- High collector to emitter voltage handling capability makes it highly versatile for most power amplification applications.
- Low base to emitter voltage, makes it easily switchable even with nominal output potentials available from linear ICs without incorporating buffer stages.
- Robust output current delivering capability makes it ideally suited for applications in power amplifiers and power inverters.
- Sturdy TO-3 case encapsulation makes it easily mountable over heatsinks with snug face to face contact, enabling perfect heat dissipation from the device and ensuring optimum response.
- Reasonable and consistent hFE gain makes it universally suitable and applicable for most purposes.
- High frequency handling range, again attributing the device with a wide range utility feature.
- The above versatility of the device in turn makes it easily replaceable with other power transistors having varied characteristics, relieving the users from the headache of searching identical compatible matches for their individual specific applications.
Let’s have a more intense and precise study regarding the above specialization of the device in the following section.
Image Courtesy - http://www.energies.alba-annuaire.fr/data/tr/2N3055.pdf
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2N3055 Datasheet Explained for Easy Reference
Before noting specific figures, readers should first become famliar with the various terminologies used on the 2N3055 spec sheet. The study of the following relevant acronyms is a must for all electronic students:
VCEO = Indicates the Collector to Emitter Breakdown voltage of the particular device, or the maximum threshold voltage level beyond which the device may get damaged or blown off. In simple words for a given device, the operations must be carried out and limited below these specified levels.
VCBO = As above, it’s the device’s Collector to Base breakdown voltage.
VEBO = It’s the Emitter to Base breakdown voltage.
hFE = DC Forward Current Gain or the efficiency of the device to amplify a given signal to appreciable limits at the collector with respect to relatively lower base biasing voltages.
IC = Collector biasing current
fT = Transition frequency or the maximum frequency rate at which the device would operate optimally.
RƟjc = Thermal withstanding capacity from the case junction, or the maximum allowable case temperature for the device, above which the device might go through a thermal run-away situation to become permanently damaged. The parameter provides the necessary data regarding the heatsink calculations for a particularly device.
PTC = Maximum allowable dissipation (heat) from the case at 25 degrees ambient temperature. Again, it’s the information through which the heatsink parameters may be calculated.
The following data provides the actual figures involved with the various 2N3055 specifications:
Polarity = NPN,
IC = 15 Amp.
VCEO = 60 Volts,
hFE = 20 (min), 70 (max) @ IC = 4 Amp, and VCE = 4 Volts,
Safe Operating Area = 2.87 Amp × 40 V for 1 second pulse.
fT = 2.5 MHz (min),
RƟjc = 1.52 degree C/W,
PTC = 115 Watts.
Now let’s study some of the important and interesting practical operations associated with 2N3055 transistors.
- slide 3 of 6
Installing or fitting 2N3055 over a heatsink: As we all know a heatsink which is meant for absorbing heat from the device, so it needs to be a very good conductor of heat and yet cheap. Aluminum is the best material used for the purpose and a conventionally accepted material as heatsinks for electronic devices. The installation of the 2N3055 would involve the following steps:
Procure from the market or fabricate the heatsink plate as per the specifications.
Drill holes as per the dimensions of the transistor leads and fixing holes, as shown in the diagram.
Apply and spread some heatsink paste over the lead side flat surface of 2N3055.
Place the component over the drilled surface so that the leads pass through the drillings appropriately, the fitting holes coincide with the drilled holes and the surfaces “stick” snugly with the heatsink paste getting tightly sandwiched between the device and the metal.
Now it’s just a matter of securing the device by nuts and screws across the concurrent holes and tightening them as firmly as possible.
Make sure the protruding leads clear pass through the center of the drillings, and is kept well aloof from the heatsink metal.
If two devices need to be fixed over a common heatsink, then make sure the heatsink mica kit is used while doing the above operations. However if their collectors (body) are in parallel then they can be directly fixed over a common heatsink metal without using mica protective insulations.
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Connecting 2N3055 Transistors in Parallel
Connecting two or more 2n3055 transistors in parallel is very easy; just join their collectors and the emitters together to produce a common terminal from the collector joint and a common terminal from the emitter joint. The base of each transistor must also be made common by joining, however each base terminal must incorporate the respective resistors (usually of identical calculated values) and the free terminal of the resistors must be joined to produce a common base connection point (refer the diagram).
Since the body of the device forms the collector, the respective connections must be acquired from the body fitting screws of the transistors.
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Making a Variable Power Supply Using Transistor 2N3055
Variable Voltage power Supply Using 2N3055 Transistor
A very reliable and efficient variable voltage and variable current power supply design can be built using a 2N3055 transistor in conjunction with a couple of other active and passive components.
The entire explanation and diagram has been already discussed in one of my previous posts; you can learn more about it HERE. Though T1 in the diagram shows a TIP 33 transistor, it can be easily replaced by a 2N3055 transistor, which will also make the circuit capable of handling higher loads.
- slide 6 of 6
Complementary Slicon Power Transistors - energies.alba-annuaire.fr/data/tr/2N3055.pdf
Authors Own Experience.
Images - By Swagatam