2N3055 transistor

[Sonia123]

Is is possible to use 2N3055 without heat sink? Also what would be the best way to connect collector (which is the metal chasis) to bread board?

 

[Grossel]

Yes, possible but not recomended.

A thin wire could be tighten to chasis with a screw.

 

[DerStrom8]

It depends on how much power you plan to dissipate with the transistor. If you plan to put a lot of current through it, you'll be dissipating more power, which means more energy is wasted in the form of heat. It is this heat for which the heat sink is used, to prevent damage to the transistor. What voltage and current do you plan to switch with the 2N3055? This will help a lot, as we can easily calculate the power and determine whether or not a heat sink is necessary.

Generally the heat sink is used as the collector, as it is already bolted to the chassis of the transistor. However, you could simply put a small bolt and nut through one of the connection holes, wrap a wire around it, and tighten it down. I have also seen some people who soldered a wire to the transistor case. It depends on what will work best for you.

I hope this helps!
Regards,
Der Strom

 

[4pyros]

Is is possible to use 2N3055 without heat sink? Also what would be the best way to connect collector (which is the metal chasis) to bread board?

I would not use it with much power on a bread board anyway. You mite melt your bread board!

 

[Sonia123]

Well the current passing through it is 2.71A with 25V. So the power would be approximately equivalent to 67.75W. So is heat sink really recommended with this power?

 

[Ziddik]

Well the current passing through it is 2.71A with 25V. So the power would be approximately equivalent to 67.75W. So is heat sink really recommended with this power?

yes, a heatsink will help the transistor from being overheat

 

[crutschow]

Well the current passing through it is 2.71A with 25V. So the power would be approximately equivalent to 67.75W. So is heat sink really recommended with this power?

Is the transistor being used in the linear mode or as a switch? There's a big difference in power dissipation between the two modes.

Certainly if it is dissipating 67.75W you will need a very large heat sink or the transistor innards will melt. After all a small soldering iron is typically only 30-40W.

 

[Nigel Goodwin]

Well the current passing through it is 2.71A with 25V. So the power would be approximately equivalent to 67.75W. So is heat sink really recommended with this power?

It's not 'recommended' it's absolutely essential - and for that amount of power would need to be VERY substantial, and preferably fan cooled.

Personally I'd probably use at least two, both on big heatsinks.

 

[4pyros]

Well the current passing through it is 2.71A with 25V.

Whats the current rating for a bread board?

 

[Nigel Goodwin]

Whats the current rating for a bread board?

Nothing like that

But assuming you were wanting to breadboard a PSU (and why would you?), then the output transistors would be mounted on an external heatsink and wired (with signal wires only) to the breadboard - all high current stuff would be off the board.

 

[4pyros]

Nothing like that

But assuming you were wanting to breadboard a PSU (and why would you?), then the output transistors would be mounted on an external heatsink and wired (with signal wires only) to the breadboard - all high current stuff would be off the board.

Yes; No high power stuff on the bread board.

 

[audioguru]

Well the current passing through it is 2.71A with 25V. So the power would be approximately equivalent to 67.75W. So is heat sink really recommended with this power?

When the transistor is passing 2.71A then why does it have a voltage across it of 25V? Usually the transistor is a switch and has a saturated voltage across it of typically only 0.2V if its base current is 271mA. Then the load dissipates 67.2W and the transistor dissipates only 0.54W and will be warm (not hot) without a heatsink.

 

[Nigel Goodwin]

When the transistor is passing 2.71A then why does it have a voltage across it of 25V? Usually the transistor is a switch and has a saturated voltage across it of typically only 0.2V if its base current is 271mA. Then the load dissipates 67.2W and the transistor dissipates only 0.54W and will be warm (not hot) without a heatsink.

Presumably it's a voltage regulator?, a VERY common use for a 2N3055 - it would be fairly rare to use a 2N3055 as a switch, it's not a good choice for it (and to be honest, it's a serious antique anyway).

 

[Dragon Tamer]

The transistor is being used as a voltage regulator. It has a forward supply voltage of 26V regulating to either 12V or 5V selectable by a switch. The regulator was designed to supply 2A of current, I'm assuming that 2.71A is an over guesstimate for that value. The transistor is actually only disipating about 28W at 12V and 42W at 5V.

I have been helping Sonia design the power supply in chat but I have no idea how to figure out the minimum necessary size of the heat sink. I am eager to know how to do this though, so anyone that can shed some light on the subject please share.

 

[audioguru]

Bits and pieces of this thread are all over the place. Some of this thread is in other threads and even in Chat. Then how are we supposed to know what is being talked about here?

 

[Dragon Tamer]

Here is the schematic if it is any help:

https://www.electro-tech-online.com/members/sonia123-albums-power-picture58484-ps6.html

 

[tvtech]

It's linear. You need an off-board cooling piece of Aluminium with the transistor fastened to it to do the job. As Nigel suggested.

Cheers,
TV Tech

 

[audioguru]

The transformer does not have a secondary voltage rating nor a power rating. It is drawn backwards.

R1 and R3 are not needed.

The value of C1 is too low.

 

[Dragon Tamer]

The transformer has an 11 to 1 ratio, it is not drawn backwards, multisim made it that way. The output voltage is 20V RMS.

 

[audioguru]

The transformer has an 11 to 1 ratio, it is not drawn backwards, multisim made it that way. The output voltage is 20V RMS.

Then Multisim is backwards.
The 20VAC is rectified into 26.3VDC. Then the 2N3055 transistor needs a proper heatsink with many fins and maybe a fan.