Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!bloom-beacon!usc!cs.utexas.edu!uunet!portal!cup.portal.com!ISW
From: ISW@cup.portal.com (Isaac S Wingfield)
Newsgroups: sci.electronics
Subject: Re: How can I turn on this bulb with TTL?
Message-ID: <20457@cup.portal.com>
Date: 15 Jul 89 04:28:32 GMT
References: <4363@merlin.usc.edu> <5769@stiatl.UUCP>
Distribution: na
Organization: The Portal System (TM)
Lines: 13

Try this:

connect TTL output directly to transistor base
connect 1K resistor from TTL output to +5V

Now, when TTL is low, it sinks 5mA, no problem
when TTL is HI, it does nothing and 1K provides
about 4-4.5 ma of base drive

be sure to use a transistor with high enough beta;
200 or so would be good

Good luck, Isaac    isw@cup.portal.com