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looking for a transistor

T

Tim Williams

Jan 1, 1970
0
MooseFET said:
The TIP35 also had a very bad dynamic saturation characteristic. When
the collector voltage got below about 2V, they slowed down to a crawl.

I've got Toshibas that slow down to a crawl below *twenty volts*.

They're video / chroma output transistors though.

Tim
 
C

ChairmanOfTheBored

Jan 1, 1970
0
IIRC, the collector is internally connected to the metal housing and the
maximum operating Tj is increased from 125-150oC to an easy 200oC with
the TO-39. Then there is the premium hermetic sealing advantage. There's
no question about the superiority of that package to all else....


If I had tried to incorporate the plastic package into the Geiger
counters we made for the Navy to look at their reactor vessel containment
areas with, we would have lost that contract, and I would have lost my
job. Since our product (The 1.5kV HV source for the counter) was fully
encapsulated, it had to be done with the right parts. Just breathing
"coffee breath" onto some assemblies can cause a premature failure.
 
E

Eeyore

Jan 1, 1970
0
ChairmanOfTheBored said:
"and the like"? You're an idiot. The metal housed device is better for
more reasons than the hermetically sealed package, idiot.

If you think that's so, then I'm sure you can name a whole list. Come on then let's
see it.

It has a much broader range of operation.

I am betting that the epoxy package peters out far sooner in designs
where the transistor's capacities are pushed.

Metal can devices are rarely used outside military and aerospace now because they
have very little to offer that's valuable in most instances.

As it happens I'm still a fan of the TO-3 can device for audio output devices since
the 2 point fixing avoids mounting flange distortion that can happen with TO-3P and
TO-264 style devices plus the higher die temperature allowable (200C instead of
150C) means they will dissipate more with the same die inside. Compare the MJL21193
(200W) and MJ21193 (250W) for example.

So, there you are. I'll use them where they have an advantage to offer. I'm
certainly not biased against them. I last used TO-18 about 35 years ago though.

Graham
 
E

Eeyore

Jan 1, 1970
0
Fred said:
IIRC, the collector is internally connected to the metal housing and the
maximum operating Tj is increased from 125-150oC to an easy 200oC with
the TO-39. Then there is the premium hermetic sealing advantage. There's
no question about the superiority of that package to all else....

The 2N2222 is in TO-18 not TO-39. TO-18 is not a useful package for power
applications.

The fact that the 2N2222 in TO-18 is only good for 500mW whilst the PN2222 is good
for 625mW DESPITE the 50C lower Tj only shows how poor the TO-18 can performs
thermally.

Graham
 
M

MooseFET

Jan 1, 1970
0
I've got Toshibas that slow down to a crawl below *twenty volts*.

They're video / chroma output transistors though.

I think I've bumped into a few like that too. IIRC they were a 500V
transistor that was normally operated in the 200V to 400V as a linear
part. It was part of a linear regulator so saturation wasn't supposed
to be happening. I noticed that when the supply voltage went low, the
regulator oscillated making a waveform that looked like a low passed
squarewave.
 
S

Spehro Pefhany

Jan 1, 1970
0
IIRC, the collector is internally connected to the metal housing and the
maximum operating Tj is increased from 125-150oC to an easy 200oC with
the TO-39. Then there is the premium hermetic sealing advantage. There's
no question about the superiority of that package to all else....

How about thermal and mechanical shock resistance?


Best regards,
Spehro Pefhany
 
C

ChairmanOfTheBored

Jan 1, 1970
0
How about thermal and mechanical shock resistance?

Since they were specifically designed originally for industrial, and
hi-rel applications, I am quite sure that they excel in both.

See abse for the Motorola specs. They were the original designers of the
part, IIRC.
 
J

John Popelish

Jan 1, 1970
0
Eeyore said:
The 2N2222 is in TO-18 not TO-39. TO-18 is not a useful package for power
applications.

The fact that the 2N2222 in TO-18 is only good for 500mW whilst the PN2222 is good
for 625mW DESPITE the 50C lower Tj only shows how poor the TO-18 can performs
thermally.

If you make a serious attempt to heat sink the TO-18, I
think you can push it harder than you can by heat sinking a
TO-92. I have seen a few TO-18s soldered to a copper plane,
or into a large plated through hole, or clamped into large
aluminum heat sink, and those could get rid of considerable
power. This was in old equipment where the choices were
TO-18, TO-39, TO-66 or TO-3. Unfortunately, this adds a lot
of capacitance to the
collector node. I think the TO-18 may even outperform the
TO-39 if properly heat-sinked, if the can construction is
the same in each (not the thick base version of the TO-39).

Heat sinking a TO-92 through the epoxy case
has a higher thermal resistance than metal to metal contact,
but at least, provides isolation between heat sink and
collector.
 
E

Eeyore

Jan 1, 1970
0
John said:
PN2222 is good for > 625mW DESPITE the 50C lower Tj only shows how
poor the TO-18 can performs thermally.

If you make a serious attempt to heat sink the TO-18, I
think you can push it harder than you can by heat sinking a
TO-92. I have seen a few TO-18s soldered to a copper plane,
or into a large plated through hole, or clamped into large
aluminum heat sink, and those could get rid of considerable
power. This was in old equipment where the choices were
TO-18, TO-39, TO-66 or TO-3. Unfortunately, this adds a lot
of capacitance to the
collector node. I think the TO-18 may even outperform the
TO-39 if properly heat-sinked, if the can construction is
the same in each (not the thick base version of the TO-39).

The data I have does not support your assertion.

The thermal resistance of the TO-18 package from junction to case is
146C/W whereas for TO-92 it is 83C/W. Will post these in abse.


Graham
 
J

John Popelish

Jan 1, 1970
0
Eeyore said:
The data I have does not support your assertion.

The thermal resistance of the TO-18 package from junction to case is
146C/W whereas for TO-92 it is 83C/W. Will post these in abse.

Thanks. I stand corrected.

Figuring out a way to hold the entire surface of the TO-92
at 25C is a bit of a problem, though. Submersion in boiling
refrigerant, perhaps (i.e. putting the transistor in the wet
end of a heat pipe). Simpler to get effective thermal
contact between a round can and a metal heat sink. But it
would be interesting to see a TO-18 operate in a heat pipe, too.
 
M

MooseFET

Jan 1, 1970
0
Thanks. I stand corrected.

Figuring out a way to hold the entire surface of the TO-92
at 25C is a bit of a problem, though. Submersion in boiling
refrigerant, perhaps (i.e. putting the transistor in the wet
end of a heat pipe). Simpler to get effective thermal
contact between a round can and a metal heat sink.

That isn't as easy as it sounds. The TO-18 is strong against
compression at the ends but not in the middle. When you attempt to
grip it, you tend to get a gap around the waist. Using a softish
alloy and making the sink have a slit in it that a screw tightened
seemed to make the best results.

The same sort of thing can be done with the TO-92 but the machining is
a bit trickier. You want the sink to press against the flat face so a
simple round hole and a slit doesn't work very well.

These days it is better to just use a bigger part.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
If you make a serious attempt to heat sink the TO-18, I
think you can push it harder than you can by heat sinking a
TO-92. I have seen a few TO-18s soldered to a copper plane,
or into a large plated through hole, or clamped into large
aluminum heat sink, and those could get rid of considerable
power. This was in old equipment where the choices were
TO-18, TO-39, TO-66 or TO-3. Unfortunately, this adds a lot
of capacitance to the
collector node. I think the TO-18 may even outperform the
TO-39 if properly heat-sinked, if the can construction is
the same in each (not the thick base version of the TO-39).

Heat sinking a TO-92 through the epoxy case
has a higher thermal resistance than metal to metal contact,
but at least, provides isolation between heat sink and
collector.


Use a hard anodized sink. That is a non-conductive interface.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
The data I have does not support your assertion.

The REALITY of decades of design incorporation of the part, however,
DOES, idiot.
The thermal resistance of the TO-18 package from junction to case is
146C/W whereas for TO-92 it is 83C/W. Will post these in abse.

U-B-Dumb. We-B-knowin-this-fact.
 
E

Eeyore

Jan 1, 1970
0
John said:
Thanks. I stand corrected.

Figuring out a way to hold the entire surface of the TO-92
at 25C is a bit of a problem, though. Submersion in boiling
refrigerant, perhaps (i.e. putting the transistor in the wet
end of a heat pipe). Simpler to get effective thermal
contact between a round can and a metal heat sink. But it
would be interesting to see a TO-18 operate in a heat pipe, too.

Well ... to be honest I don't see either package as suitable for serious
power dissipation.

Graham
 
E

Eeyore

Jan 1, 1970
0
ChairmanOfTheBored said:
Use a hard anodized sink. That is a non-conductive interface.

On TO-18 ?

You're quite mad. So, it'll dissipate about 1W now !

Graham
 
E

Eeyore

Jan 1, 1970
0
ChairmanOfTheBored said:
The REALITY of decades of design incorporation of the part, however,
DOES, idiot.

Designs that fail to use the correct data are flawed designs.

Graham
 
C

ChairmanOfTheBored

Jan 1, 1970
0
Well ... to be honest I don't see either package as suitable for serious
power dissipation.


No one said they were, dope.

They are only good for 1 W or less, and that is pushing it.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
On TO-18 ?

You're quite mad. So, it'll dissipate about 1W now !

Graham
There are mil spec heat sinks that are hard anodized that clamp or are
thermally bonded right onto the can.

It will dissipate 1W in free air.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
Designs that fail to use the correct data are flawed designs.

Graham

That must have been what happened to you then.
 
E

Eeyore

Jan 1, 1970
0
ChairmanOfTheBored said:
Eeyorewrote:

That must have been what happened to you then.

NO.

Let's face it. You're no designer.

Graham
 
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