Driving 220/330 terminated loads

Steve Thatcher melamy at earthlink.net
Sun Dec 3 15:44:05 CST 2006

the normal totem pole output for S TTL logic will only sink 20 ma to 
guarantee a logic low. The 220 ohm resistor to +5 will be 22.7ma, so 
you are exceeding the chip's capability by some amount. LS and HCT 
can sink even less current.

best regards, Steve Thatcher

At 01:02 PM 12/3/2006, you wrote:
>I know the "right" answer to this one--you drive 220/330 ohm
>terminated loads with 7438-type OC drivers.  But, going a bit afield
>from "correct", can one drive a single 220/330 ohm terminated load at
>the end of a 3m length of ribbon cable at 1 MHz using plain old totem-
>pole STTL output?  How about an LSTTL or HCT totem-pole driver?
>You can assume that the receiver is a 74LS14.

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