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Octal Darlington Transistor IC Question? ULN2903AN?
I have a couple of questions about how this IC will operate. I guess I actually want to know more about a couple of the pins. (Data Sheet link below)
1. Obviously there are eight "Base" and eight "Collector" pins. Is the "Common" acting as the common "Emitter?" (please explain if you can)
2. What would the "Ground" pin be used for? Isn't that what the Emitter is usually attached to?
3. Are the internal diodes used to as a bias for linking in parallel?
http://focus.ti.com/lit/ds/symlink/uln2803a.pdf
Anything else useful you might be able to tell me. Thanks!
1. and 3. The Common connection goes to the supply positive voltage. The clamping diodes are normally reverse biased (off) but provide a current path for relay inductance "kick-back" that would otherwise create a destructive voltage that damages the transistors.
2. Ground is the negative supply connection and input return.
