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OT: SOT-523 PNP Question

I need something like a 2N3906 device in an SOT-523 package BUT with pin-out:

1 = Base 2 = Collector 3 = Emitter

A client screwed up his PCB layout and has _only_ 5600 boards to patch... by Tuesday :-(

Possibly doesn't exist, but I told him I'd try... he's near a nervous breakdown. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

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| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Reply to
Jim Thompson
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Reform the leads of some MMBT2907's. It will take a lot of labor.

Why did he build 5600 boards without testing a first article? He deserves a nervous breakdown.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

I know. But he's a PhD, so what can I say ?>:-} He says they worked when tested, but I suspect they "worked" long enough to fry the device... C-E interchange with 9V across it :-( ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)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.
Reply to
Jim Thompson

It may have worked, with modest reverse beta. Some PNPs have high b-e breakdown voltages, 12 volts maybe.

He might just find a transistor that works that way. But not by Tuesday.

Why not cut and jumper? Make him do it himself, all 5600 boards.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

MMBT3906 datasheet says VEBOmax = 5V. I have the client running some breakdown tests for me as soon as he gets back to his Hong Kong offices in the morning.

It may happen, though I have an add-a-component fix that is easier than R&R... just slobber on top >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)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.
Reply to
Jim Thompson

Most SOT-523 PNPs have the same pinout. Without knowing the circuit, could a P-channel mosfet, or P-channel JFET be used that may have the desired pinout?

The SOT-523 is quite a small device. I'd hate to have to do any mod work on it!

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk
Reply to
Mike Perkins

Ph.D's love to learn things. This will certainly be a great lesson.

boB

Reply to
boB

See attached drawing. Drawing is looking at bottom of 3906; red is rotated position. Note 2 leads can be soldered on board and the 3rd fiddled with added wire. Not the best "fit" in the world and highly dependent on layout and PCB spacing.

Alternate solution: make a 2-sided flex (or similar) small PCB that does the scramble. At that quantity, the scramble patch board could be pick&placed with glue and reflowed, then the 2N3906 pick&placed for 2nd reflow. Neater results, if part layout is tight, this may be the only way.

Charge extra for the solution that you recommend.

Reply to
Robert Baer

Are the boards already assembled?

Reply to
Cydrome Leader

Yep :-( But it's not going to be too bad... I've found several alternate solutions that eliminate the PNP... and the labor is on mainland China. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)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.
Reply to
Jim Thompson

I've solved that problem on prototype boards by straightening the part leads then mounting it upside down with blobs of solder. That's probably not a good solution for 5600 boards. I'm not sure that Robert's solution isn't better.

How big of a hole does he need to bury 5600 boards?

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

As far as i have seen, ALL of the "specs" for bipolars are 5 volts, and that clearly is a lie. Most have a typical breakdown in the 8V region,some are higher.

Reply to
Robert Baer

Do share the fix when it's final.

Reply to
Cydrome Leader

I know, that why I asked the client to use a real scope and get me some measurements. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)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.
Reply to
Jim Thompson

Replaced a switchable current mirror (overkill) with a pull-up resistor O:-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)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.
Reply to
Jim Thompson

Who designed the original circuit to start with?

Jamie

Reply to
Maynard A. Philbrook Jr.

BUT... upside down only interchanges pins 1 & 2; the callout you gave has pins 2 & 3 interchanged.

Too bad the parts are in place - would have to be removed before my flex PCB "patch" was placed..

Reply to
Robert Baer

Like i said, upside down does not interchange pins 2 & 3.

Reply to
Robert Baer

Who else... the PhD, natch!

Reply to
Robert Baer

Too many people fall in love with current mirrors and think that they can make good ones from discrete transistors. We even had an example of that here, not too long ago.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

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