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I'd like to use PBSS4350SS transistors for driving multiple low power solenoids, but looking at the datasheet I can't figure out what value the base resistor (R1) should be?

schematic

simulate this circuit – Schematic created using CircuitLab

Mika Rauhala
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  • If you do a site search for "Base Resistor" you can see this question has been asked a lot of times before. Here's a link to a good answer https://electronics.stackexchange.com/a/125246/103993 –  Aug 22 '18 at 08:30

1 Answers1

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Work out the current through L1, roughly 12V divided by its resistance.

Divide this by the minimum transistor gain from the data sheet, this gives you a minimum value for the base current.

The voltage across R1 is 3.3V-transistor VBE or about 2.6V.

Divide this by the base current to give you the maximum value of R1, in practice you need lower this by about 10% to ensure the transistor is driven into saturation.

RoyC
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