SOT23 PNP Specific Pinout
leumasyerrp wrote 06/05/2018 at 02:03 • 0 pointsI have spent a few hours searching for SOT23 PNP transistors that have the following pinout: 1-Base, 2-Collector, 3-Emitter for driving a common anode 7-segment display. I made a mistake on my schematic and now have 4 PCBs that I would like to try to salvage. If I can find transistors with the footprint above they should drop right in. Just wondering if anyone has heard of such an animal. All of the SOT23 PNP transistors I have looked at on Digi-Key are BEC. I can always get new PCBs but if there happens to be a drop in fix that would be helpful as I prototype the circuit.
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The display is multiple digits so I am using the PNP transistors to switch the digits and then I have NPN transistors on the cathodes for the segments. I have it working just took an ugly bodge job that I was hoping to clean up with different pinout PNPs. Thanks.
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"Common Anode" are you sure you want PNP?
http://ee.hawaii.edu/~sasaki/EE361/Fall06/Lab/7disp.html
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I was able to bodge them on one PCB by standing the package up on its end and used two bits of small wire (https://cdn.hackaday.io/images/4453541528156579026.jpg). But it is unstable at best and a pain and would not be fun for more then one PCB. One wire as suggested would be nice.
I will have to try these suggestions, thanks everyone.
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Looks like you could have done it by lining up 2 of the pins (B & C) and use 1 wire for E.
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I've soldered SOT23 transistors upside-down and diagonally to solve a similar problem before. They're such small parts that it isn't hard to bridge the gap with solder.
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If there is enough room on the PCB, just rotate it 180°, so that you can solder E and C the right way, then use a wire to solder B.
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If you can afford a 0.7V drop, you might be able to get away with NPNs as emitter followers to boost the current instead of PNPs as saturated switches. Then the BEC pinout should work.
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