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transistor 2n3055

B

Bob Clark

The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Thanks for the help.

Bob Clark
 
M

Meat Plow

The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Thanks for the help.

Bob Clark

Power amps, pass filter.
--
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COOSN-266-06-25794
 
J

John Popelish

Bob said:
The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing?

There is no such thing as a typical use. Transistors are
used in all sorts of applications. The collectors are
connected to cases because of the way transistors are made
from slices of silicon. The slice becomes the collector,
and the base and emitter are formed as islands on one side
by successive masking, doping, heat treatment and
metalization steps. Then the slice is bonded to the metal
part of the case for heat sinking, as well as electrical
connection to the collector, and flying leads are bonded to
the top surface to make connection to the emitter and base
islands.
The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

The leads are not connected to make sense, they are
connected in the only way that is feasible from a
manufacturing standpoint.
 
M

Michael Black

Bob Clark" ([email protected]) said:
The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.
Many/most power transistors are not common emitter.

For instance, in a power supply the power transistor is used to
pass the voltage to the output, so the collector is connected to
the "raw" voltage source, and the emitter is the output. The transistor
needs to supply current, it doesn't need to do any real voltage amplification.

In power amplifiers, it is rare to see a common emitter configuration.
(You'd see them in the early days of transistors, but not in decades.)
Again, the collector goes to the positive supply, and the emitter is
connected to the output (and usually there is a complementary PNP transistor
doing the mirror image to the negative supply voltage). The power output
transistors do not need to supply much voltage gain, earlier stages
take care of that, but the output transistors do have to supply current,
and with a low output impedance. You won't get that with a common emitter
configuration.

Since in neither case neither the collector nor emitter are grounded, it
doesn't particularly matter which is connected to the case. It may be
convenient, in terms of internal arrangement, to have the collector
connected to the case.

Michael
 
C

Chuck

Bob said:
The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Thanks for the help.

Bob Clark

Hey Bob, a Google search on 2N3055 gives
720,000 hits. There's a world of
fascinating information out there on the
web.

81,000 hits from a search on "2N3055
circuit"!

That's a skill you need to master.

Good luck.

Chuck
 
B

Bob Clark

When seeing an NPN transistor used in a circuit, as a switch, the load is
usually connected to "VCC", the current goes from +, through the load
resistance, then to the collector, through the NPN transistor, and out the
emitter to ground. Wouldn't it be nice if the transistors in the TO3 case
had the emitter connected to the TO3 case which we could ground to the
apparatus case. But since the transistors in the TO3 case are the reverse
of this, one has to isolate the TO3 case from ground so as to be able to use
an NPN transistor in the TO3 case. Maybe John Popelish is right, this is
the only way a transistor can be made in the TO3 case. Hard to believe!!!

Thanks, Bob Clark
 
J

John Larkin

When seeing an NPN transistor used in a circuit, as a switch, the load is
usually connected to "VCC", the current goes from +, through the load
resistance, then to the collector, through the NPN transistor, and out the
emitter to ground. Wouldn't it be nice if the transistors in the TO3 case
had the emitter connected to the TO3 case which we could ground to the
apparatus case. But since the transistors in the TO3 case are the reverse
of this, one has to isolate the TO3 case from ground so as to be able to use
an NPN transistor in the TO3 case. Maybe John Popelish is right, this is
the only way a transistor can be made in the TO3 case. Hard to believe!!!

Thanks, Bob Clark

The collector is the chip substrate, and they solder that to the can
to let the heat out. The emitter and base leads are on the top of the
chip, so are connected to the pins by wire bonds. That's how most
planar silicon transistors (and mosfets) work.

GaAs fets are nice for RF, because the source is the substrate and is
convenient to bolt to a big grounded heatsink. I think there are some
silicon npn RF transistors that have grounded emitters soldered to the
case.

John
 
E

Eeyore

Bob said:
The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case

It's only grounded if the case is grounded. In any case (lol) you may very well
not want the current to flow to chassis/frame. Most power devices are isolated
from chassis.

, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground,

No they're not.

and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit?

How about a quasi-complementary audio output stage ? Google it.

What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Not especially.

What makes sense is that the back of the transistor die is the collector and
when soldered to a heatsink, the heatsink tab or header also becomes the
collector connection.

Graham
 
E

Eeyore

Bob said:
When seeing an NPN transistor used in a circuit, as a switch,

As a switch and only as a switch. Think amplifier instead of switch.

the load is
usually connected to "VCC", the current goes from +, through the load
resistance, then to the collector, through the NPN transistor, and out the
emitter to ground.

No. To the negative supply (power return). Not ground.

Wouldn't it be nice if the transistors in the TO3 case
had the emitter connected to the TO3 case which we could ground to the
apparatus case.

It would be no more convenient at all. In fact case to collector is better since
where multiple devices are used in parallel the collectors tend to be commoned
and the heatsink does that for you.

But since the transistors in the TO3 case are the reverse
of this, one has to isolate the TO3 case from ground so as to be able to use
an NPN transistor in the TO3 case. Maybe John Popelish is right, this is
the only way a transistor can be made in the TO3 case. Hard to believe!!!

It's true. Most of the bulk of the die (chip) is collector.

Graham
 
J

John Popelish

Bob said:
Maybe John Popelish is right, this is
the only way a transistor can be made in the TO3 case. Hard to believe!!!

Hey, back when the TO-3 case was first designed and planer
transistors were something pretty new, They were just
tickled to have a high power package with a big transistor
in it.

But the difficulty of isolating and mounting it, especially
with high voltage on the collector, or with low capacitance
to a heat sink, it fairly quickly was realized that
something better would have to be designed. The power tab
TO-220 (pin compatible with the TO-66, the smaller version
of the TO-3) and TO-218 (pin compatible with the TO-3) and
all their variants, carry most of the trade, today, that
isn't surface mount.

But all but very specialized devices still have the
collector to the heat sink surface, because that is the way
planer transistor die are still made.
 
J

Jamie

Bob said:
The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Thanks for the help.

Bob Clark
Unity gain amplifiers (current boosters), just about anything a
large transistor can do..

The case style does not govern the electrical use of the part other
than maybe physical placement and heat dissipation.

You use a mounting kit that gives you an insulated sheet etc..
 
S

sparky

When seeing an NPN transistor used in a circuit, as a switch, the load is
usually connected to "VCC", the current goes from +, through the load
resistance, then to the collector, through the NPN transistor, and out the
emitter to ground. Wouldn't it be nice if the transistors in the TO3 case
had the emitter connected to the TO3 case which we could ground to the
apparatus case. But since the transistors in the TO3 case are the reverse
of this, one has to isolate the TO3 case from ground so as to be able to use
an NPN transistor in the TO3 case. Maybe John Popelish is right, this is
the only way a transistor can be made in the TO3 case. Hard to believe!!!

Thanks, Bob Clark

Ever hear of insulators? They make em all the time and can be used
to isolate the transistor case from the heat sink. When you learn how
to design transistor circuits you will also learn how to physically
mount
the devices.
 
P

Phil Allison

"John Popelish"
Hey, back when the TO-3 case was first designed and planer transistors
were something pretty new, They were just tickled to have a high power
package with a big transistor in it.

But the difficulty of isolating and mounting it, especially with high
voltage on the collector, or with low capacitance to a heat sink, it
fairly quickly was realized that something better would have to be
designed. The power tab TO-220 (pin compatible with the TO-66, the
smaller version of the TO-3) and TO-218 (pin compatible with the TO-3) and
all their variants, carry most of the trade, today, that isn't surface
mount.


** Nonsense.

Plastic " flat pack " power devices are not " better " than TO3 - they
are merely cheap and nasty substitutes.

TO3 pack devices are now mostly found in professional / industrial
equipment, on grounds of their higher reliability and where low cost is not
so crucial.




........ Phil
 
R

Ross Herbert

The transistor 2N3055 is packaged in a TO3 case. It has its collector
"grounded" to the case, and the base and emitter to the two pins. NPN
transistors are usually used with the emitter going directly to ground, and
the collector somewhere far from ground. Can someone give me a typical
application for this 2n3055 transistor, showing how it is typically used in
a circuit? What am I missing? The MJ2955, it's mating PNP, is the same
way, and this, in a PNP makes sense.

Thanks for the help.

Bob Clark


I'm not sure, but you seem to be labouring under the misconception
that since the collector of the NPN die is connected directly to the
case, this constitutes an electrical "grounding". If it were mounted
directly to a metal heatsink without isolation washers and insulator
pad, and depending upon the connections to the base and emitter, it
might result in fatal destruction of the device or other associated
circuitry. Provided that any heatsink is isolated from circuit
"ground" then you can mount them directly to a heatsink without
insulation and no problems will arise, but in most situations this is
not the case. As long as the three terminals C - B - E are connected
as per a well designed circuit there will be no deleterious
interaction and the device will perform as intended.

As to applications - there are many and varied and you should do some
Googling.
 
E

Eeyore

Phil said:
"John Popelish"


** Nonsense.

Plastic " flat pack " power devices are not " better " than TO3 - they
are merely cheap and nasty substitutes.

Agreed. The single mounting hole is alone cause for concern since it is
realtively tricky to ensure a good thermal path. I use a large diameter washer
on top of the device to help with this.

TO3 pack devices are now mostly found in professional / industrial
equipment, on grounds of their higher reliability and where low cost is not
so crucial.

The same die can be reliably run at a higher Tj in a metal can too. This gives
extra power rating.

A guy I used to work with annoyed the f**k out of me by insisting that we had to
use TO-3Ps because he said they were (a) cheaper and (b) because everyone uses
them now (as if that was a reason).

When I actually checked On-Semi's site, the TO-3 device is *CHEAPER* !!!!

http://www.onsemi.com/PowerSolutions/product.do?id=MJ21193 $2.17 for 250W
(0.87 cents/W)

http://www.onsemi.com/PowerSolutions/product.do?id=MJL21193 $2.40 for 200W
(1.2 cents /W)

It's also easier to cool metal can devices since they can operate at higher
temps.


Graham
 
C

cdd

Agreed. The single mounting hole is alone cause for concern since it is
realtively tricky to ensure a good thermal path. I use a large diameter washer
on top of the device to help with this.


The same die can be reliably run at a higher Tj in a metal can too. This gives
extra power rating.

A guy I used to work with annoyed the f**k out of me by insisting that we had to
use TO-3Ps because he said they were (a) cheaper and (b) because everyone uses
them now (as if that was a reason).

When I actually checked On-Semi's site, the TO-3 device is *CHEAPER* !!!!

http://www.onsemi.com/PowerSolutions/product.do?id=MJ21193 $2.17 for 250W
(0.87 cents/W)

http://www.onsemi.com/PowerSolutions/product.do?id=MJL21193 $2.40 for 200W
(1.2 cents /W)

It's also easier to cool metal can devices since they can operate at higher
temps.

Graham- Hide quoted text -

- Show quoted text -

The 2n3055 was very common in audio amps in mid 80's- about 50w with
two and about 100w with 4 on the output stage-quite rugged transistors
really
 
J

John Larkin

Agreed. The single mounting hole is alone cause for concern since it is
realtively tricky to ensure a good thermal path. I use a large diameter washer
on top of the device to help with this.

The really big die simply won't fit into the antique TO-3 can, and the
wirebond situation is awkward. The clamp-mount (no hole) TO-247's are
much better.
A guy I used to work with annoyed the f**k out of me by insisting that we had to
use TO-3Ps because he said they were (a) cheaper and (b) because everyone uses
them now (as if that was a reason).

Off-center packages, like TO-220 and TO-3P, are pretty bad.
It's also easier to cool metal can devices since they can operate at higher
temps.

The chip is the limit, not the epoxy.

John
 
E

Eeyore

John said:
The really big die simply won't fit into the antique TO-3 can, and the
wirebond situation is awkward. The clamp-mount (no hole) TO-247's are
much better.

Really ? Those must be damn big dies in that case !

them now (as if that was a reason).

Off-center packages, like TO-220 and TO-3P, are pretty bad.

What do you prefer ?

The chip is the limit, not the epoxy.

That's not what On Semi says.

The TO-204AA (TO-3) MJ21193/4 and the plastic TO-3P (TO-264) MJL21193/4 use the same
die but it's derated in the plastic package.

Tj max = 150C in plastic vs 200C in TO-3.


Graham
 
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