Integrated Circuit. Transistor Transistor Logic (TTL). 4−Line−to−16−Line Decoder /Demultiplexer. 24−Lead DIP Type Package. Description: The NTE is a. 1) CPD is defined as the value of the IC’s internal equivalent capacitance which is calculated from the operating current consumption without load. (Refer to Test . datasheet, circuit, data sheet: NSC – 4-Line to Line for Electronic Components and Semiconductors, integrated circuits, diodes, triacs.
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4 Line to 16 Line Demultiplexer / Decoder
I have a doubt in the demultiplexer section. This is the image of a 1 to 16 demux.
I understand how it works. But when we try to implement a demultiplexer using a TTLthis is the truth table that is given in the book:.
Why are the outputs inverted? Is the hardware implementation circuit different than the one explained in theory? If you have some experience using BJTs you will know that NPN transistors are best used ci pull a signal to 0V common emitter, with the output connected to the collector and quite weak at pulling a signal high.
Common collector, with the signal connected to the emitter, which remains at 0.
So TTL circuitry adopted asymmetric logic levels, where ‘0’ was guaranteed to be below 0. This carried through to the datasgeet current requirements: And this carried through to the way the logic was used, and designed with. Inputs were pulled high by default, and only pulled low when necessary, to save power.
So you can use a 47 kilohm resistor to pull up drops 1. Dstasheet speed signals were usually active low, for much the same reason. And that’s what is going on with the It is counterintuitive yes, but it is a well-established convention that the sort of devices that this part will be controlling will have active-low enable inputs.
(PDF) 74154 Datasheet download
This all has to do with the actual ic design. So theory will cover only the theory which explains the basic functionality of the working of a demultiplexor. The actual implementation of the chosen ic has active low outputs.
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Why is the output in the truth table inverted in a ic used as a demux? But when we try to implement a demultiplexer using a TTLthis is the truth table that is given in the book: The datasheet of these components is always the key to the correct implementation. Sign up or log in Sign up using Google. Sign up using Facebook.