> I wish to drive a IR LED at 40khz

BTW, you can use a 555 (or any gated oscillator) to do most
of the work

http://home.clear.net.nz/pages/joecolquitt/irtx2.gif

It (a) modulates your data with 40kHz, so you simply supply the
0s and 1s, and (b) has much better current capability (+/-300mA)
than a PIC pin

Joe
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