Interfacing TTL and CMOS logic

[KA4HJH]

>I need to drive a logic CMOS IC from a TTL source (actually a port of a
>8051).
>The power supply of the TTL source is +5V, while the CMOS IC is +15V.
>Of course, direct interfacing is impossible, especially because the
>'positive' level of the TTL
>output (typically 3.5V) is not sufficient for the CMOS. So I need to put
>some buffer in between.

Sounds like a job for something with an open collector output. That would
invert the signal, though. You'd need two in series. Two transistors would
work in a pinch. Quick and dirty.

Terry Bowman, KA4HJH
"The Mac Doctor"