2N3904 maximum ratings Vceo Vcbo

[Bill Bowden]

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?




--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Cursitor Doom]

On Sat, 02 May 2015 19:45:51 -0700, Bill Bowden wrote:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60
volts. When the transistor switches off, the collector to emitter
voltage will be 48 and the base voltage will be near 0 through a
resistor. Any problems with that?

Why not just use a snubber diode across the inductor and be sure?

 

[John Larkin]

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
<bperryb@bowdenshobbycircuits.info> wrote:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?

As long as the base is not floating (the Vceo case) you'll be OK.

The base-grounded case is sometimes denoted Vcer (b-e resistor) or
Vcex (shorted), and is about equal to Vcbo.

Keep the base resistor low, like 1K or something.


--

John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jim Thompson]

On Sun, 03 May 2015 10:55:18 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> wrote:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


As long as the base is not floating (the Vceo case) you'll be OK.

The base-grounded case is sometimes denoted Vcer (b-e resistor) or
Vcex (shorted), and is about equal to Vcbo.

Keep the base resistor low, like 1K or something.

BVcbo = Collector-to-base breakdown, emitter open
BVceo = Collector-to-emitter breakdown, base open
BVcer = Collector-to-emitter breakdown, base-to-emitter resistor
BVces = Collector-to-emitter breakdown, base-to-emitter shorted
BVcex = Collector-to-emitter breakdown, base-to-emitter reverse biased

etc

See..

<https://www.onsemi.com/pub/Collateral/AN1628-D.PDF>

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[DecadentLinuxUserNumeroUn]

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
<bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?

Absolutely presents a problem...

This will let the smoke out. No question.

 

[John Larkin]

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
<DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jim Thompson]

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.

Depends on the load-line... a snubber of some sort might be necessary.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[DecadentLinuxUserNumeroUn]

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
<jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.

Pretty fucking unprofessional statement, Larkin.

I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

 

[John Larkin]

On Thu, 07 May 2015 14:06:55 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.

Depends on the load-line... a snubber of some sort might be necessary.

...Jim Thompson

Not the classic load line, but if there's an unclamped inductive load,
the flyback could be hundreds of volts.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
<DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.

I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.

A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!

Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jim Thompson]

On Fri, 08 May 2015 12:52:17 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?

Depends >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[John Larkin]

On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 12:52:17 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?

Depends >:-}

...Jim Thompson

Thanks for that input.

We stock a really cute 30mm 12-volt Sunon fan. It starts spinning
around 3 volts and works fine at 20, as far as I dared to go.

What's weird is that, at 15 volts, if you stall it, usually it won't
start. If I then drop the supply a couple of volts, it starts spinning
again.

It's probably OK at 15, since I don't expect anybody to stall it, but
it's weird. We'll get some 24 volt versions to test.

Possibly the FPGA guy did something silly, like using a zillion
registers instead of a RAM. The FPGA seems to be awfully hot, given
that we're not doing all that much and the main clock is only 64 MHz.
It would sure be easier to change some VHDL instead of adding a fan.

Seems like half my hassles lately are thermal.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jim Thompson]

On Fri, 08 May 2015 13:29:55 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 12:52:17 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?

Depends >:-}

...Jim Thompson

Thanks for that input.

We stock a really cute 30mm 12-volt Sunon fan. It starts spinning
around 3 volts and works fine at 20, as far as I dared to go.

What's weird is that, at 15 volts, if you stall it, usually it won't
start. If I then drop the supply a couple of volts, it starts spinning
again.

It's probably OK at 15, since I don't expect anybody to stall it, but
it's weird. We'll get some 24 volt versions to test.

Possibly the FPGA guy did something silly, like using a zillion
registers instead of a RAM. The FPGA seems to be awfully hot, given
that we're not doing all that much and the main clock is only 64 MHz.
It would sure be easier to change some VHDL instead of adding a fan.

Seems like half my hassles lately are thermal.

Fan motor's voltage range is pretty much dependent on how they do the
commutation. Here's the beasty...

<http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg>

that I designed a controller for... Bosch Motor (Bühlertal),
ultimately into a Mercedes A/C blower... nasty speed control
specifications plus it had to pass a noise test... chief engineer put
head into the ductwork and commutation noise couldn't be audible ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[John Larkin]

On Fri, 08 May 2015 15:42:59 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 13:29:55 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 12:52:17 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?

Depends >:-}

...Jim Thompson

Thanks for that input.

We stock a really cute 30mm 12-volt Sunon fan. It starts spinning
around 3 volts and works fine at 20, as far as I dared to go.

What's weird is that, at 15 volts, if you stall it, usually it won't
start. If I then drop the supply a couple of volts, it starts spinning
again.

It's probably OK at 15, since I don't expect anybody to stall it, but
it's weird. We'll get some 24 volt versions to test.

Possibly the FPGA guy did something silly, like using a zillion
registers instead of a RAM. The FPGA seems to be awfully hot, given
that we're not doing all that much and the main clock is only 64 MHz.
It would sure be easier to change some VHDL instead of adding a fan.

Seems like half my hassles lately are thermal.

Fan motor's voltage range is pretty much dependent on how they do the
commutation. Here's the beasty...

http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg

Our fan is tiny, 30x30x10 mm. Awfully cute.

that I designed a controller for... Bosch Motor (Bühlertal),
ultimately into a Mercedes A/C blower... nasty speed control
specifications plus it had to pass a noise test... chief engineer put
head into the ductwork and commutation noise couldn't be audible ;-)

...Jim Thompson

Correction: the fan appears to be smarter than I am.

If the fan is stalled, at any voltage, it pulls current for about a
second and then shuts down. It starts up if the voltage changes
significantly, or after a roughly 10 second delay.

It quits spinning at about 23 volts but recovers if the voltage is
reduced. Sunon calls it a 12 volt fan but has no min/max specs.

There must be a lot of logic inside that tiny fan.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jim Thompson]

On Fri, 08 May 2015 16:03:20 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 15:42:59 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 13:29:55 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Fri, 08 May 2015 12:52:17 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 12:19:38 -0700, John Larkin
jlarkin@highlandtechnology.com> wrote:

On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Thu, 07 May 2015 13:51:28 -0700, John Larkin
jlarkin@highlandtechnology.com> Gave us:

On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno
DLU1@DecadentLinuxUser.org> wrote:

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

That's only 8 volts above the Vceo spec. No problem.


Pretty fucking unprofessional statement, Larkin.

I pointed out to him that he should not leave the base open, which is
what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt
application, but if he already has them, the risk of using them is
nil.

Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We
don't have any in stock.


I ran two to drive the front end of my HV switcher drives into
transformer.

One designs within the spec, not over it, dipshit.

One designs things that work and can be sold.



A 1N4001 can do 1000V, but there is no way I would use them in a
multiplier.

Too slow, mostly. And thru-hole axial!


Folks spec EL and even solid state caps at just over half their rated
voltage. You seem to not even know, much less understand why.

Sometimes I derate caps, and sometimes I use them at over their rated
voltages. Low voltage ceramic caps can stand 10x or 20x their rated
voltages; you just lose capacitance. Tantalums can run at rated
voltage in some cases, or should be derated 3:1 in others.

We were just yesterday discussing how much power we can dissipate into
standard surface-mount resistors. It's safe to go way over their
ratings if you put decent power pours on the end caps.

Datasheet specs are sort of arbitrary anyhow.

Speaking of which, I have 15 volts available. Should I use a 12 volt
fan, or a 24 volt fan?

Depends >:-}

...Jim Thompson

Thanks for that input.

We stock a really cute 30mm 12-volt Sunon fan. It starts spinning
around 3 volts and works fine at 20, as far as I dared to go.

What's weird is that, at 15 volts, if you stall it, usually it won't
start. If I then drop the supply a couple of volts, it starts spinning
again.

It's probably OK at 15, since I don't expect anybody to stall it, but
it's weird. We'll get some 24 volt versions to test.

Possibly the FPGA guy did something silly, like using a zillion
registers instead of a RAM. The FPGA seems to be awfully hot, given
that we're not doing all that much and the main clock is only 64 MHz.
It would sure be easier to change some VHDL instead of adding a fan.

Seems like half my hassles lately are thermal.

Fan motor's voltage range is pretty much dependent on how they do the
commutation. Here's the beasty...

http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg

Our fan is tiny, 30x30x10 mm. Awfully cute.


that I designed a controller for... Bosch Motor (Bühlertal),
ultimately into a Mercedes A/C blower... nasty speed control
specifications plus it had to pass a noise test... chief engineer put
head into the ductwork and commutation noise couldn't be audible ;-)

...Jim Thompson

Correction: the fan appears to be smarter than I am.

If the fan is stalled, at any voltage, it pulls current for about a
second and then shuts down. It starts up if the voltage changes
significantly, or after a roughly 10 second delay.

It quits spinning at about 23 volts but recovers if the voltage is
reduced. Sunon calls it a 12 volt fan but has no min/max specs.

There must be a lot of logic inside that tiny fan.

You can put an awfully large amount of smarts into a small chip. The
size only goes up with the current handling.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[jfeng@my-deja.com]

On Friday, May 8, 2015 at 4:45:53 PM UTC-7, Bill Bowden wrote:

I thought the specs indicated "guaranteed" performance? Vceo
of 40 would imply every device would meet that spec plus a
little more?

I would expect the answer to this question would depend on the date code. A part from the 1980s made by diffusion would probably have a very wide range of propeerties, both within a lot and lot-to-lot. Something made in the 21st century by ion implantation might have a very tight range, and could be manufactured with very little "safety margin".

Why do you raise the question? Is it academic curiosity, or do you havee a specific application and lots of 2N3904s in the warehouse? The 2N3904 is cheap (about 10 cents is smalll hobbyist quantities), so a part with a sufficiently higher BV is probably less than 20 cents in large manufacturing quantities. You would have to sell a lot of widgets to recover the additional engineering cost of using an underspec'd part.

 

[Bill Bowden]

"DecadentLinuxUserNumeroUno" <DLU1@DecadentLinuxUser.org> wrote in message
news:14jnkal3sg1hncthrdmnn9q8kvqonfpf42@4ax.com...

On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems
with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

I thought the specs indicated "guaranteed" performance? Vceo of 40 would
imply every device would meet that spec plus a little more? It's a resistive
load, so there aren't any inductive considerations. And the base will be
grounded to the emitter through a 3K resistor when the collector voltage is
48.






--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Phil Hobbs]

On 5/8/2015 7:45 PM, Bill Bowden wrote:

"DecadentLinuxUserNumeroUno" <DLU1@DecadentLinuxUser.org> wrote in message
news:14jnkal3sg1hncthrdmnn9q8kvqonfpf42@4ax.com...
On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden"
bperryb@bowdenshobbycircuits.info> Gave us:

Is it safe to operate a 2N3904 in a switching application with a supply
voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts.
When the transistor switches off, the collector to emitter voltage will be
48 and the base voltage will be near 0 through a resistor. Any problems
with
that?


Absolutely presents a problem...

This will let the smoke out. No question.

I thought the specs indicated "guaranteed" performance? Vceo of 40 would
imply every device would meet that spec plus a little more? It's a resistive
load, so there aren't any inductive considerations. And the base will be
grounded to the emitter through a 3K resistor when the collector voltage is
48.

The collector-base leakage rises steeply with V_CB. With the base left
open, it gets multiplied by beta, so I_C goes through the roof at a
lower voltage. If you prevent the B-E junction from getting
forward-biased, e.g. by shorting B-E, it holds up out to V_CES, which is
higher. A resistor isn't quite as good, and reverse bias is a bit
better, so you have a family of breakdown voltages rather than just one.

V_CEO < V_CER < V_CES < V_CEX .

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

John Larkin <jlarkin@highlandtechnology.com> wrote:

It's probably OK at 15, since I don't expect anybody to stall it, but
it's weird. We'll get some 24 volt versions to test.

Toss in a couple of 1N4001s (or surface-mount equal) in series with the
fan connector and get on down the road.

Yes, I usually write software for a living... why are you looking at me
funny?

> Seems like half my hassles lately are thermal.

Pic somewhat related: https://xkcd.com/451/ , especially the first
panel.

Matt Roberds