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

[signalman72]

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*)]

No, generally it is not acceptable to do this in the normal "common emitter" configuration you'll likely use.

 

[cjdelphi]

Not without maxing out the current from 4017 from each pin

 

[signalman72]

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.