[time-nuts] HP5328A LEDS driver transistor
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Jan 23 17:27:32 EST 2012
>The 5328A manual I have shows a 3.5 V supply (looks like it is used just
>for the display). But with a bit lower Vce sat drops, I'd guess you
>1 V across the 10 ohm segment resistors. Or only about 900 mA when all
>9 segments are on (but at a low duty cycle). Did HP also use a 5 V version
>of the driver in some 5328A counters?
Interesting. I have 3 different sets of schematics for the
5328A. The most legible of these (thus the one I consult first)
shows a 5 V supply for the display. The other two show 3.5 V, as
yours does. I cannot recall ever measuring the display supply
voltage in a 5328.
Even with 900 mA per digit, I'd want a transistor with >/=2 A maximum
collector current for the digit drivers -- so I still think the
ZTX949 may be the best readily-available choice.
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