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Few examples of logic devices
Here we list functional diagrams of few logical ICs with
the brief description of what they do and also little note
on technology advancements
Buffer (non-inverting):
What is buffer?
These devices boost/amplify signal power capabilities by
raising the current capacity (both source and drain) but keeping
the logic voltage levels same as inputs.
Where used (application): Buffers are used when there requirement
to drive multiple devices or higher load device from a single
logical output (microcontroller output or any other such logical
signal generator). Good example can be you can't connect an
LED directly to the output of microcontroller port, buffer
can be put in between LED and microcontroller's port.
There are many types of buffers available in the market here
below is the connection diagram of 74LCX244.
Connection Diagram
3 to 8 decoder:
What is 3 to 8 decoder?
Decoders have 3 inputs and 8 outputs. The binary
input fed at input will be decoded to provide either logical
high or low on one of the 8 outputs, which is termed as octal
equivalent for that binary input. For a binary input 100,
which is 4 in octal number system, the output pin called O4
will go either high or low.
Where used (application): Is used in memory address decoder
or any such decoders. Good example is, if a microcontroller
has only 8 outputs but you may have to control 32 devices,
you can go for this device for such application.
Below is functional diagram and truthtable of one popular
decoder 74VHC138 from Fairchild
Based on the required logic functions, building circuits
is very easy, you just need to know pin diagram from the datasheet.
you hardlly need any other discrete components. So that's
the reason only function diagram is given instead of circuit
diagrams in this page.
To know other types of logic families please
visit the following urls:
http://www.fairchildsemi.com/products/logic/
http://www.st.com/stonline/products/families/logic_signal_switch/logic_signal_switch.htm
http://www.onsemi.com/PowerSolutions/taxonomy.do?id=612
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