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Driving the base of a transistor with the output of a 4017

signalman72

Jan 26, 2014
57
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Jan 26, 2014
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Is it acceptable to just directly drive the base of a BJT(s) from the outputs of the 4017 decade counter, or should I use a resistor before the BJT? I plan on using the 3904. Thanks in advance.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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Jan 21, 2010
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25,510
No, generally it is not acceptable to do this in the normal "common emitter" configuration you'll likely use.
 

signalman72

Jan 26, 2014
57
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Jan 26, 2014
Messages
57
Thanks for the replies. I used a 1k resistor before the 3904. I'm powering the 4017 with a 9 volt battery. The current draw of the 3904 with the resistor is about 6.5 mA, so I'm safe. Without it was a little over 20 mA.
 
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