All Questions
Tagged with ttl digital-logic
16
questions
5
votes
3
answers
1k
views
IC takes no input (or high) as high and low input as low on breadboard
I was working with IC 7400 (or LM74LS00 / NAND) (and IC 7486 - XOR) to design and verify combination circuits and logic gates.
Consider the lower end of breadboard as LOW (connected to GROUND) and ...
14
votes
4
answers
2k
views
What logic family is best for general-purpose hobbyist stuff?
I need to buy a few logic ICs. Which family should I get? HC? HCT? Which kind is best to have lying around in a parts box, for maximum compatibility with unpredictable future projects? Wide supply ...
- 28.9k
10
votes
6
answers
41k
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Rising edge pulse detector from logic gates
The circuits I describe are entirely made of 7400 series logic gates (7402, 7404 and 7408 ic).
I'm trying to build a rising (positive) edge pulse detector using logic gates.
The following circuit ...
- 309
25
votes
8
answers
5k
views
What are the advantages of using FPGAs over TTL in intro computer architecture?
I teach the one and only computer architecture course at a liberal arts college. The course is required for the computer science major and minor. We do not have computer engineering, electrical ...
- 1,619
3
votes
3
answers
2k
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How do TTL NAND gates work?
This is supposed to be a simple NAND gate.
I understand how the output is 1 if one of the inputs is zero
but if both inputs are 1 then the base of Q1 is supposed to be zero. This is what I don't ...
3
votes
3
answers
5k
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Why is the output (in the truth table) inverted in a ic 74154 used as a demux?
I am studying Digital Principles and Applications from Malvino and Leach. I have a doubt in the demultiplexer section. This is the image of a 1 to 16 demux. I understand how it works.
So, if ABCD = ...
- 33
11
votes
4
answers
4k
views
Should I use CMOS vs. TTL?
Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere.
So yeah, CMOS and ...
- 1,947
6
votes
2
answers
14k
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Help between 2n2222 and 2n2222a?
I am thinking about ordering this:
http://www.ebay.com/itm/x100-Fairchild-PN2222A-2N2222A-NPN-Small-Signal-TO-92-Transistors-US-Seller-/171520659038?pt=LH_DefaultDomain_0&hash=item27ef6d8e5e
and ...
- 81
5
votes
2
answers
2k
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CMOS (or CMOS compatible) shift register with latched open-drain outputs
I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this ...
- 32k
4
votes
2
answers
3k
views
Which logic families interpret a floating input as a definite value?
From what I remember, from decades ago, 1980's 5v TTL chips would see a floating input as a zero (because they switched on current, rather than voltage). Update: it seems they were interpreted as ...
- 982
4
votes
2
answers
19k
views
TTL, Totem Pole vs. Open Collector Output
What is the difference of these two ttl nand gates?
What is a totem pole, what does it do and what is it used for?
When connecting multiple ttl logic gates together is it better to use one or the ...
- 53
2
votes
3
answers
2k
views
Which 74xx logic families are overvoltage tolerant on their outputs?
Here's my dilemma: I have a 3.3v active-low logic line, and I want to use it to drive a 5v active-low logic line. The 5v line already has a pullup, so my plan was to use an open-collector buffer IC ...
- 7,749
2
votes
4
answers
3k
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74181 ALU not working properly cascaded to add 8 bit numbers
I'm trying to make a homebrew CPU but having problems with the 74LS181 ALU, which I'm simulating in Logisim software before diving into real ICs and breadboards.
I've cascaded two 74181 following ...
- 171
1
vote
3
answers
2k
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2xAAA battery => 3.3v/250mA step-up converter with logic-driven power control [superseded]
EDIT: The requirements in the question below appear to be practically unsolvable, but happily after a bit of digging I actually found an alternative equivalent RS232 device which runs off a 3.7V Li-Po ...
- 227
0
votes
1
answer
2k
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STM32F407 CMOS or TTL or HC
I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this ...
- 907