TO-3 cases can dissipate more power, but are more complex to mount since the pins have to go through the heatsink. The corresponding need to use a thin enough heatsink flange area to allow this often offsets the extra dissipation capability of the case, and thus you're at a zero-sum situation.
TO-247s are easier to mount and dissipate enough heat to get the job done, so they're becoming the TO-3's replacement for many applications. If you can get a transistor in either form, the 247 will be easier to work with especially if you're using large flat heatsinks that don't include a mounting flange or dedicated mounting area for a TO-3 device - in these cases you'd have to MAKE the flange and thermally connect it to the heatsink, and this is hardly the optimal way of doing things.
oO
TO-247s are easier to mount and dissipate enough heat to get the job done, so they're becoming the TO-3's replacement for many applications. If you can get a transistor in either form, the 247 will be easier to work with especially if you're using large flat heatsinks that don't include a mounting flange or dedicated mounting area for a TO-3 device - in these cases you'd have to MAKE the flange and thermally connect it to the heatsink, and this is hardly the optimal way of doing things.
oO
In terms of heatsinking, TO-3 is better (for the same amount of dissipated power/heat). But in all cases I found, the equivalent TO-247 package produces better sound.
But I don't think that heatsinking capability should be something to consider for this purpose. Unless you want to drive the transistor close to its limit (in case of a bipolar, a second breakdown voltage?), e.g. a class-A with limited heasink?
don't confuse TO-3 with TO-3p
just a "by the way".
TO3's take 2 screws, TO-247 only one so they are a bit less expensive to mount.
just a "by the way".
TO3's take 2 screws, TO-247 only one so they are a bit less expensive to mount.
And you can easily use clamp or just a bar of aluminium to mount them on the heatsink. This is more convenient than using screws.
(and they look better...)
(and they look better...)
TO-3P?
Is the TO-247 the same size package as the plastic variant TO-3P, which is what Hitachi calls their plastic package for the 2SK1058?
I'm just wondering because I'm presently working in Protel on my pcb and will have to draw the footprint unless I can find a similar size one.
Thanks,
Bart.
Is the TO-247 the same size package as the plastic variant TO-3P, which is what Hitachi calls their plastic package for the 2SK1058?
I'm just wondering because I'm presently working in Protel on my pcb and will have to draw the footprint unless I can find a similar size one.
Thanks,
Bart.
TO-3P
Thanks jackinnj, I was just comparing them actually. I think they are virtually the same, bar some minor differences around the corners.
Thanks jackinnj, I was just comparing them actually. I think they are virtually the same, bar some minor differences around the corners.
TO-3
Well I.ve used TO-3s but not TO-247. The reason Im asking is that Im planning to replace my amps output transistors which are 2n3055 to to-247 transistor (maybe 2sc5200 or c3281) for better power handling and heat transfer since to-247 have impressive datasheets. However now im hearing that to-3s are still a choice when thermal management is an issue.
Maybe i should just use mj15003 or mj15024?
Well I.ve used TO-3s but not TO-247. The reason Im asking is that Im planning to replace my amps output transistors which are 2n3055 to to-247 transistor (maybe 2sc5200 or c3281) for better power handling and heat transfer since to-247 have impressive datasheets. However now im hearing that to-3s are still a choice when thermal management is an issue.
Maybe i should just use mj15003 or mj15024?
Did you realize, that not just the case of most TO3 is magnetic, but also all base and emitter pins.
OMG!! MAGNETIC! RUN FOR THE HILLS!!! 🙂 There is something sexy-cool about TO-3 devices that the plastic devices are lacking in, regardless of sound (or magnitism...lol!)
Certainly sound quality must be first on the list when designing something, but asthetic considerstions also count. And there are few things prettier than a pile of paralleled TO-3 devices on a hefty heatsink out there for all to see.
...Except tubes glowing in their All-Mighty (see God Of Triodes 
) Greatness.
Face it. Cold steel can't compare with hot tungsten and clear glass, especially that dusted in a haze of blue glow.
Tim
) Greatness.Face it. Cold steel can't compare with hot tungsten and clear glass, especially that dusted in a haze of blue glow.
Tim
--TO-3 or TO-247?
What is a good rule of thumb
for determining how many TO-3's
you need vs. TO-247 when paralleling
output stages.
Example,
suppose a design calls for 8
TO-247 packages paralleled,
but you found the same part
in T0-3 case, how many TO-3's
would you use now to be
equivalent in heat dissipation
to the 247 package.
The reason I ask is;;;
There are some manufacturers
who brag about T0-3 package usage
in their amplifiers but they don't use
that many in the design whereas a
similar amplifier design may use more
247 packages.
What is a good rule of thumb
for determining how many TO-3's
you need vs. TO-247 when paralleling
output stages.
Example,
suppose a design calls for 8
TO-247 packages paralleled,
but you found the same part
in T0-3 case, how many TO-3's
would you use now to be
equivalent in heat dissipation
to the 247 package.
The reason I ask is;;;
There are some manufacturers
who brag about T0-3 package usage
in their amplifiers but they don't use
that many in the design whereas a
similar amplifier design may use more
247 packages.
"how many TO-3's would you use now to be equivalent in heat dissipation to the 247 package."
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Personally, I would consult the particuluar device specs to see what its capable of. In theory though you should be able to use the same number of either style device.....
Mark
___________________________________________________
Personally, I would consult the particuluar device specs to see what its capable of. In theory though you should be able to use the same number of either style device.....
Mark
"Face it. Cold steel can't compare with hot tungsten and clear glass, especially that dusted in a haze of blue glow."
__________________________________________________
Actually my Aleph 2's have a wonderful blue glow inside them that your tube amps could never equate to.......
Mark
__________________________________________________
Actually my Aleph 2's have a wonderful blue glow inside them that your tube amps could never equate to.......
Mark
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