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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The active-low enable inputs allow cascading of demultiplexers over many bits.

Understand, this is a typical example of application, not it’s sole purpose. High speed signals were usually active low, for much the same reason. Common collector, with the signal connected to the emitter, which remains at 0.

Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Will someone please explain the purpose of inverting the outputs 0 through 15 as well as the use the NAND gates here? WhatRoughBeast 49k 2 28 Please consider upvoting those questions you found useful like this one by clicking the arrow pointing up near the answer vote count which is in turn above the checkbox you clicked to accept this question.

This is the image of a 1 to 16 demux. Sign up using Facebook.

Datasheet(PDF) – National Semiconductor (TI)

Email Required, but never shown. When either strobe input is high, all outputs are high. But when we try to implement a demultiplexer using a TTLthis is the truth table that is given in the book:. Many TTL parts and older memory chips have active low enable inputs, so the active low outputs of this kc can be connected directly to those inputs. Why are the outputs inverted?


The demultiplexing function is performed by using the 4 input lines to address the output line, passing data from one of the strobe inputs with the other strobe input low. There are probably two enable inputs because otherwise there would be two unused pins on the 24 pin package I don’t recall seeing 22 pin DIP packages. If you want to know exactly what is going on then draw out the truth table, but it is unlikely their function will make much sense to you.

National Semiconductor

So you can use a 47 kilohm resistor to pull up drops 1. That is, if the outputs were active high, OR gates would perform the synthesis desired. Since the ouputs are active low, NAND gates do the datazheet. Sign up using Email and Password.

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All the other ouputs stay high. Email Required, but never shown. Why is the output in the truth table inverted in a ic used as a demux? Each or these 4-line-toline decoders utilizes TTL circuitry to decode four binary-coded inputs into one of sixteen mutually exclusive outputs when both the strobe inputs, G1 and G2, are low. For example, if the target application requires 16 7-segment LED displays, but your microcontroller only has 4 lines to select which display is active, this chip 74LS would provide a very effective method of essentially multiplying you selecting lines by a 4 times.


I understand how it works. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Post as a guest Name. The active-low output is just how the design for that specific decoder was carried out – there is also active-high varieties.

Home Questions Tags Users Unanswered. If you have some experience using BJTs you will know that NPN transistors are best used to pull a signal to 0V common emitter, with the output connected to the collector and quite weak at pulling a signal high. You can upvote more than one answer. If you wanted to generate a 1 of demultiplexer, you could use 16 s looking at the 4 least significant bits, while a single would look at the 4 most significant bits, with one ouput going to each of the other 16 s.

The LED can be chosen at random by the status of the 4 line selector inputs. This allows more flexibility in the logic functions daatasheet. 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. This carried through to the input current requirements: