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Tri switch buffers are used for

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May 15, 2015
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Tri-state buffers/line drivers are used to prevent buss line ringing and loading down the output pins of multiple TTL/CMOS chips. What else do tri-state buffer prevent or do. What TTL or CMOS chips need to use a Tri-state buffer?

Depends on the circuit requirements.
When it is desirable to fully isolate I/O tristate works.

I have seen tri-state buffers on dataline busses, address busses, control busses and I/O busses.

What other logic IC components need to use a tri-state buffer before their input pins and after on their output pins

Tri-state is only used on outputs, and may/must be used wherever two or more outputs are connected to the same signal/ input.

If you connect two outputs together they will 'short' when they are different, making an undefined state for the input. Using tri-state buffers makes it possible to enable one output at the time, driving the signal properly.

Tri-state buffers increase the noise immunity to prevent false triggering. The tri-state buffers use hysteresis in their input structure to reduce the noise. Totem pole outputs from multiple IC chips can not be wired or tied together. You have to use tri-state buffers when using totem pole outputs. Open collector outputs can be wired ORed or ANDed which doesn't cause conflict or contentions with multiple outputs tied to a bus or common node. I have seen tri-state buffers cause buss contenting problems much more then using Wired Ored or wired ANDed contenting issues of outputs in conflict. Using a tri-state buffer increases the noise immunity and try's not to use buss contenting issues.

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