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[EE] 2n3904 pulse current

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madscientistatlarge

[EE] 2n3904 pulse current

Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum pulse width 1ms? I want to use them for the common cathode drivers driving 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case). The spec sheet says 200 mA continuous and I can't find pulse information. Thanks.

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Bob Blick-5

Re: [EE] 2n3904 pulse current

The current gain of a 2N3904 is already tanking at 100mA(hfe = 30) so it looks like a poor choice for your proposed application.

Best regards, Bob

________________________________________
From: [hidden email] <[hidden email]> on behalf of madscientistatlarge
Sent: Friday, May 29, 2020 1:50 PM
To: [hidden email]
Subject: [EE] 2n3904 pulse current

Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum pulse width 1ms? I want to use them for the common cathode drivers driving 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case). The spec sheet says 200 mA continuous and I can't find pulse information. Thanks.

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Jason White-20

Re: [EE] 2n3904 pulse current

In reply to this post by madscientistatlarge

For hobbyist work you can get away with it. Especially if you are willing
to tolerate shortened component lifespan, and the risk that difficult
batches of parts behave differently.

For professional work: I would advise against it.

NXP MMBT3904 datasheet (2004 Feb 03)
(1) abs. max peak collector current is 200mA
(2) on figure 2-5 as collector current approaches 200mA, current gain
approaches zero. Above that current the thermal load due to low gain/poor
performance gets concerning.

On Friday, May 29, 2020, madscientistatlarge <
[hidden email]> wrote:

> Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum
> pulse width 1ms? I want to use them for the common cathode drivers driving
> 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case).
> The spec sheet says 200 mA continuous and I can't find pulse information.
> Thanks.
>
>
> Sent with ProtonMail Secure Email.
>
>
>
> --
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> http://mailman.mit.edu/mailman/listinfo/piclist
>

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madscientistatlarge

Re: [EE] 2n3904 pulse current

In reply to this post by Bob Blick-5

Thanks, I was beginning To realize I probably want a darlington.

Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, May 29, 2020 3:06 PM, Bob Blick <[hidden email]> wrote:

> The current gain of a 2N3904 is already tanking at 100mA(hfe = 30) so it looks like a poor choice for your proposed application.
>
> Best regards, Bob
>
> From: [hidden email] [hidden email] on behalf of madscientistatlarge
>
> Sent: Friday, May 29, 2020 1:50 PM
> To: [hidden email]
> Subject: [EE] 2n3904 pulse current
>
> Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum pulse width 1ms? I want to use them for the common cathode drivers driving 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case). The spec sheet says 200 mA continuous and I can't find pulse information. Thanks.
>
>
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

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Spehro Pefhany

Re: [EE] 2n3904 pulse current

In reply to this post by madscientistatlarge

I would suggest a 2N4403, or perhaps an S8550 if you want to support the beleaguered Asian electronics industry.

Sent from a Microsoft, Android or Apple device
(Either mobile or desktop)

> On May 29, 2020, at 4:57 PM, madscientistatlarge <[hidden email]> wrote:
>
> Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum pulse width 1ms? I want to use them for the common cathode drivers driving 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case). The spec sheet says 200 mA continuous and I can't find pulse information. Thanks.
>
>
> Sent with ProtonMail Secure Email.
>
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

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madscientistatlarge

Re: [EE] 2n3904 pulse current

That looks like a good one. Also I'm discovering a darlington array won't work for me, between the Vce of the cathode darlington, and the anode driver, and the led drop leaves too little voltage and too much variation to control the current with a resistor. With a single bipolar pair for each digit I'll have some head room (fortunately I'm running the atMEGA at 5V)

Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, May 29, 2020 4:28 PM, Spehro <[hidden email]> wrote:

> I would suggest a 2N4403, or perhaps an S8550 if you want to support the beleaguered Asian electronics industry.
>
> Sent from a Microsoft, Android or Apple device
> (Either mobile or desktop)
>
> > On May 29, 2020, at 4:57 PM, madscientistatlarge [hidden email] wrote:
> > Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum pulse width 1ms? I want to use them for the common cathode drivers driving 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case). The spec sheet says 200 mA continuous and I can't find pulse information. Thanks.
> > Sent with ProtonMail Secure Email.
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
> --
>
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> View/change your membership options at
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madscientistatlarge

Re: [EE] 2n3904 pulse current

In reply to this post by Spehro Pefhany

I need npn, to sink current on the common cathode of each digit. Otherwise that looks good. Looks like I'll wind up using BC33740BU, good minimum gain and nice low saturation voltage with reasonable drive. I've already picked the pnp for the segment/dp drivers of the string.

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, May 29, 2020 4:28 PM, Spehro <[hidden email]> wrote:

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mike brown

Re: [EE] 2n3904 pulse current

In reply to this post by madscientistatlarge

Why don't you use some low rdson logic level mosfet? Is cost an issue? Is
size an issue? Is this battery powered?

On Fri, May 29, 2020, 17:55 madscientistatlarge <
[hidden email]> wrote:

> That looks like a good one. Also I'm discovering a darlington array won't
> work for me, between the Vce of the cathode darlington, and the anode
> driver, and the led drop leaves too little voltage and too much variation
> to control the current with a resistor. With a single bipolar pair for
> each digit I'll have some head room (fortunately I'm running the atMEGA at
> 5V)
>
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Friday, May 29, 2020 4:28 PM, Spehro <[hidden email]> wrote:
>
> > I would suggest a 2N4403, or perhaps an S8550 if you want to support the
> beleaguered Asian electronics industry.
> >
> > Sent from a Microsoft, Android or Apple device
> > (Either mobile or desktop)
> >
> > > On May 29, 2020, at 4:57 PM, madscientistatlarge
> [hidden email] wrote:
> > > Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum
> pulse width 1ms? I want to use them for the common cathode drivers driving
> 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case).
> The spec sheet says 200 mA continuous and I can't find pulse information.
> Thanks.
> > > Sent with ProtonMail Secure Email.
> > > --
> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
> >
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> --
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> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

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madscientistatlarge

Re: [EE] 2n3904 pulse current

I'll check those out. Cost is a slight issue. I was a little concerned about esd, but I guess these would be less sensitive than some of the smaller fets. Guess I should just stop being chicken, I'm already using fets to drive soldering irons. It's for my use and mental exercise designing, building, and making work. Cost is always an issue for me, very small fixed income but lots of brains, time, decent design skills, and I really like design work, and I'll get to actually code a microcontroller (not worried about that part!).

Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, May 29, 2020 5:20 PM, mike brown <[hidden email]> wrote:

> Why don't you use some low rdson logic level mosfet? Is cost an issue? Is
> size an issue? Is this battery powered?
>
> On Fri, May 29, 2020, 17:55 madscientistatlarge <
> [hidden email]> wrote:
>
> > That looks like a good one. Also I'm discovering a darlington array won't
> > work for me, between the Vce of the cathode darlington, and the anode
> > driver, and the led drop leaves too little voltage and too much variation
> > to control the current with a resistor. With a single bipolar pair for
> > each digit I'll have some head room (fortunately I'm running the atMEGA at
> > 5V)
> > Sent with ProtonMail Secure Email.
> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > On Friday, May 29, 2020 4:28 PM, Spehro [hidden email] wrote:
> >
> > > I would suggest a 2N4403, or perhaps an S8550 if you want to support the
> > > beleaguered Asian electronics industry.
> > > Sent from a Microsoft, Android or Apple device
> > > (Either mobile or desktop)
> > >
> > > > On May 29, 2020, at 4:57 PM, madscientistatlarge
> > > > [hidden email] wrote:
> > >
> > > > Can a 2n3904 handle 320mA pulses at less than 10% duty cycle, maximum
> > > > pulse width 1ms? I want to use them for the common cathode drivers driving
> > > > 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst case).
> > > > The spec sheet says 200 mA continuous and I can't find pulse information.
> > > > Thanks.
> > >
> > > > Sent with ProtonMail Secure Email.
> > > >
> > > > -----------------------------------
> > > >
> > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > View/change your membership options at
> > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > >
> > > --
> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
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mike brown

Re: [EE] 2n3904 pulse current

ZVN4206A is a to94 case and should work good for you with 5V on the gate,
should have less than 1 ohm resistance at 300mA and 5V on the gate, less
than 2 ohm's with 3.3V. Just don't buy them from Amazon unless you want to
pay a ridiculous price. You should be able to get them for under $1US
each.

I'm sure there are others out there. TO220 package devices are easy to
find too, with pretty high current capabilities. I like using mosfets for
low side switches.

On Fri, May 29, 2020, 18:45 madscientistatlarge <
[hidden email]> wrote:

> I'll check those out. Cost is a slight issue. I was a little concerned
> about esd, but I guess these would be less sensitive than some of the
> smaller fets. Guess I should just stop being chicken, I'm already using
> fets to drive soldering irons. It's for my use and mental exercise
> designing, building, and making work. Cost is always an issue for me, very
> small fixed income but lots of brains, time, decent design skills, and I
> really like design work, and I'll get to actually code a microcontroller
> (not worried about that part!).
>
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Friday, May 29, 2020 5:20 PM, mike brown <[hidden email]> wrote:
>
> > Why don't you use some low rdson logic level mosfet? Is cost an issue? Is
> > size an issue? Is this battery powered?
> >
> > On Fri, May 29, 2020, 17:55 madscientistatlarge <
> > [hidden email]> wrote:
> >
> > > That looks like a good one. Also I'm discovering a darlington array
> won't
> > > work for me, between the Vce of the cathode darlington, and the anode
> > > driver, and the led drop leaves too little voltage and too much
> variation
> > > to control the current with a resistor. With a single bipolar pair for
> > > each digit I'll have some head room (fortunately I'm running the
> atMEGA at
> > > 5V)
> > > Sent with ProtonMail Secure Email.
> > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > > On Friday, May 29, 2020 4:28 PM, Spehro [hidden email] wrote:
> > >
> > > > I would suggest a 2N4403, or perhaps an S8550 if you want to support
> the
> > > > beleaguered Asian electronics industry.
> > > > Sent from a Microsoft, Android or Apple device
> > > > (Either mobile or desktop)
> > > >
> > > > > On May 29, 2020, at 4:57 PM, madscientistatlarge
> > > > > [hidden email] wrote:
> > > >
> > > > > Can a 2n3904 handle 320mA pulses at less than 10% duty cycle,
> maximum
> > > > > pulse width 1ms? I want to use them for the common cathode drivers
> driving
> > > > > 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst
> case).
> > > > > The spec sheet says 200 mA continuous and I can't find pulse
> information.
> > > > > Thanks.
> > > >
> > > > > Sent with ProtonMail Secure Email.
> > > > >
> > > > > -----------------------------------
> > > > >
> > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > View/change your membership options at
> > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > >
> > > > --
> > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > View/change your membership options at
> > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > >
> > > --
> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
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> > View/change your membership options at
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>
>
>
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madscientistatlarge

Re: [EE] 2n3904 pulse current

In reply to this post by mike brown

Excellent suggestion, the FDN359BN are more than adequate, and only about $0.10 more than the bipolars I was going to use.

Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, May 29, 2020 5:20 PM, mike brown <[hidden email]> wrote:

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Richard Graziano

Re: [EE] 2n3904 pulse current

try 2N6731 NPN also 350mA TO92
Rich

On Fri, May 29, 2020 at 11:28 PM madscientistatlarge <
[hidden email]> wrote:

> Excellent suggestion, the FDN359BN are more than adequate, and only about
> $0.10 more than the bipolars I was going to use.
>
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Friday, May 29, 2020 5:20 PM, mike brown <[hidden email]> wrote:
>
> > Why don't you use some low rdson logic level mosfet? Is cost an issue? Is
> > size an issue? Is this battery powered?
> >
> > On Fri, May 29, 2020, 17:55 madscientistatlarge <
> > [hidden email]> wrote:
> >
> > > That looks like a good one. Also I'm discovering a darlington array
> won't
> > > work for me, between the Vce of the cathode darlington, and the anode
> > > driver, and the led drop leaves too little voltage and too much
> variation
> > > to control the current with a resistor. With a single bipolar pair for
> > > each digit I'll have some head room (fortunately I'm running the
> atMEGA at
> > > 5V)
> > > Sent with ProtonMail Secure Email.
> > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > > On Friday, May 29, 2020 4:28 PM, Spehro [hidden email] wrote:
> > >
> > > > I would suggest a 2N4403, or perhaps an S8550 if you want to support
> the
> > > > beleaguered Asian electronics industry.
> > > > Sent from a Microsoft, Android or Apple device
> > > > (Either mobile or desktop)
> > > >
> > > > > On May 29, 2020, at 4:57 PM, madscientistatlarge
> > > > > [hidden email] wrote:
> > > >
> > > > > Can a 2n3904 handle 320mA pulses at less than 10% duty cycle,
> maximum
> > > > > pulse width 1ms? I want to use them for the common cathode drivers
> driving
> > > > > 7 segment display, 12 digits multiplexed (7 seg+DP@40mA ea. worst
> case).
> > > > > The spec sheet says 200 mA continuous and I can't find pulse
> information.
> > > > > Thanks.
> > > >
> > > > > Sent with ProtonMail Secure Email.
> > > > >
> > > > > -----------------------------------
> > > > >
> > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > View/change your membership options at
> > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > >
> > > > --
> > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > View/change your membership options at
> > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > >
> > > --
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> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
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> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
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> http://mailman.mit.edu/mailman/listinfo/piclist
>

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