I've assembled JTAG ICE clone from this schematics:
(I'm aware of it's limitations: no AVRStudio 5 support and limit number of MCU with JTAG).
My JTAG ICE is always powered from USB via FT232RL board I've already have. I'd like to add jumper to be able to power target from JTAG ICE (like usbtinyISP).
Additionally I want to put 74HC244 buffer (http://eldigi.ru/site/programmators/download/74HC244.pdf) on JTAG lines. I've heard that JTAG is picky about line driving characteristics. What I should consider while adding this buffer? Do I really need it for 3.3V targets?