How Can I Use a Transistor to Drive a Relay with a Negative Output?

[triden]

Hey guys,

Right now I have a circuit designed and seems to work fairly well. Now the output from my circuit is a negative output and I need it to drive a relay. The relay I am using says it draws about 100mA and my chip will output 50mA max. I figured I would put a transistor on the output to drive my relay...the only problem is that the output is negative. In this case I am not sure what to do. Do I need an PNP instead of an NPN?

So far I figure the IC neg output goes to base, emitter to ground side of coil and collector to ground rail of circuit...but I don't think this will trigger because the base is negative.

Thanks for your suggestions

 

[es]

By negative, I assume you mean negative logic. (Not that it outputs a voltage below ground). If this is the case
http://www.rason.org/Projects/transwit/transwit.htm
see figure 3

 

[berkeman]

If your circuit pulls low, drive a PNP transistor in series with an NPN transistor, which pulls low again at a higher current.