@Graynomad - Hfe is 130 @ 2A and 80 @ 3A, so I'm estimating I should be able to get at least 100 @ 2.4A. The data sheet on the 74ac138 (http://www.fairchildsemi.com/ds/74/74AC138.pdf
) says it can provide up to 50mA; in another thread (http://arduino.cc/forum/index.php/topic,72866.msg547333.html
) Crossroads said it should be able to do 24mA.
I think you're right, if I measure current from a TLC5916's ground pin I'd hope to see about 800mA (8 outputs @100mA ea) but my current meter only goes up to 500mA. I know I need a new meter but am trying to figure out if I should get a new basic multimeter, or if there's something fancier that would let me measure these pulses.
@Magician - sorry if I was unclear. The output pins from the 74ac138s are connected to 43 ohm resistors, which are connected to the bases of the DPLS350Y transistors. I'm using the formula from "Choosing a suitable transistor" at http://www.kpsec.freeuk.com/trancirc.htm
; Rb = (Vc x hFE) / (5 x Ic), so (5 x 100) / (5 x 2.4) = 500 / 12 = 41.67.