Re: Can base amperage on an NPN be negative, and still work?

Mr. J D wrote:
I am using a couple of AND gates to turn on transistors. The datasheets
say it can output a max of -24mA at HIGH. I am attaching the output to
a 1K resistor - then to- the base of a NPN transistor. Does the
potential amperage need to be positive in order to turn on(saturate)
the transistor?

I think you are getting confused by datasheets. When it says '-24mA'
for Ioh (for which there will be a Voh specified, incidentally) it
means the current is going into the device (from an electron flow
perspective).

Look at the current - from an electron flow view, the current will
enter the emitter, move through the base and go through the output
stage of the gate to the positive power supply.

So assuming you are running your logic from +5V, then it will operate a
NPN just fine, and a 1k base resistor should be fine as well.

Cheers

PeteS

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