Questions tagged [7400]

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What is the output type of the 74AHC594?

What is the output type of the 74AHC594 IC? I didn't find the answer in this datasheet. There is stated in some datasheets for the 74594 IC from other manufacturers that the output type is buffered. ...
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1answer
50 views

What are the additional transistors used for in this hex inverter?

I'm learning about electronics and was studying the SN7404 hex inverter schematic when I saw this: I naively expected just a single transistor (the one in the bottom right) and the input at the base ...
2
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2answers
101 views

What's the difference between 74LS00 “gates” and 74LS37 “buffers”?

The TI 74LS00 is "quadruple 2-input positive-NAND gates" and the 74LS37 is "quadruple 2-input positive-NAND buffers." The pinouts are identical. The LCCC package is documented exactly the same for ...
0
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1answer
41 views

Unpowered 74ls chips vs Powered Nano?

I have a power-hungry 74ls digital logic project that I want to connect a USB-connected Arduino Nano to, but I'm not sure how design the interface between them safely. The project has an external 5V ...
0
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1answer
105 views

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 ...
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1answer
138 views

HC vs LVC for 3.3V Logic

I am designing a circuit in which Vdd=3.3V. I have checked datasheets of hex inverters 74HC04 and 74LVC04 and both of these can work good at 3.3V logic circuits. If I have to select one of them then ...
0
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1answer
238 views

Clock signal generator using 7400

I have an old PCB that uses this clock generator (means I'm absolutely sticking to the schema). The IC is standard 7400, resistors are the same, but the capacitors I'm using have 470 uF (500's are ...
2
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2answers
133 views

Using 74HC154 with LEDS current resistor

I am using a 74HC154 to control 10 LEDs in a design. Since only one LED will be on at a time I wanted to use one resistor rather than a resistor per LED. Is there any difference between the two ...
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1answer
146 views

Atari Punk Console with 7400 chips?

How would I create a stepped tone generator using 7400 logic? For the first part, it's easy to have same range generator, with an additional transistor. Is there any way to make the same range a ...
3
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4answers
2k views

10k Resistor Pull Up/Down Standard for 74 series chips

I've been having some issues lately with the usage of 10k ohm resistors as pull down resistors for 74ls series chips. Most people seem to choose 10k resistors as their default pull up/down value but I'...
5
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2answers
4k views

74LS vs. 74HC series ICs for Ben Eater's 8-bit Computer

What are the primary differences between 74LS series and 74HC series ICs? I know that LS series are TTL and HC are CMOS, but beyond that what are the key differences? For example, Ben Eater uses LS ...
9
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3answers
660 views

How can I implement a very simple asynchronous DRAM controller?

I'd like to know how to build a bare bones asynchronous DRAM controller. I have some 30-pin 1MB SIMM 70ns DRAM (1Mx9 with parity) modules that I'd like to use in a homebrew retro computer project. ...
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0answers
18 views

Controlling two things with a tri-state output using discrete logic [duplicate]

I'm trying to control a bunch of MOSFETs with an Arduino microcontroller, and was wondering if it would be possible to control two FETs with one tri-state Arduino output. There are three states that ...
0
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2answers
202 views

Why does the potentiometer have no effect on the output voltage here?

I have the circuit below, where D and Q are input and output pins (respectively) of a 74373 octal D-type transparent-latch IC. As I vary the pot from 0-10k when D is high, the voltage goes high and ...
4
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1answer
2k views

7405 TTL Chip outputting nothing when given low input

I’m struggling learning how to use some of these components for a lab. One thing I noticed is that when giving the 7405 hex inverter a low input, the output when checked by my logic probe shows there’...
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2answers
190 views

7400 chip register with common in/out pins

First of all, I don't know if this kind of question is allowed here, so sorry if it isn't. I am looking for a 7400 series register which has common in and out pins (like for the RAM ou EEPROM: ) with ...
1
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1answer
1k views

LTSpice: 74HCT Library - Setting 74HCT74 D F/F Initial State

I am using the 74HCT library from the Yahoo user group. I currently have two 74HCT74 D flip-flops in my circuit but I do not know how to set their initial state (Q = LOW for both). Is this done in a ...
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2answers
134 views

7408 AND Gate, Odd Behaviour

I'm putting together a simple DTACK circuit for a 68k homebrew machine, and part of that is requires me to know when either the Upper Data Strobe (UDS) or Lower Data Strobe (LDS) is asserted LOW. I've ...
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2answers
496 views

How does an output switching from HI or LO to HI-Z effect an input in CMOS?

Let's say we have a tri-state buffer output connected to an inverter input, implemented in 7400 series CMOS chips. If the buffer output is HI, the inverter output is LO. If the buffer output is LO, ...
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4answers
121 views

What are the available solutions for a 8-input OR function that is 74xx compatible?

I need to implement an 8-input OR function that is compatible to IC chips of the 7400 series. I already found a few solutions, but none of them is perfect. A perfect solution would be an OR-gate chip ...
0
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1answer
454 views

Why is there no open-collector OR-gate in the 7400 series? [closed]

I searched in the "List of 7400 series integrated circuits" on Wikipedia for a open-collector OR-gate, but couldn't find any. The list looks complete, so I assume there is no such chip in the 7400 ...
0
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1answer
197 views

Why do some logic gate chips have a reversed pin layout?

I am using some logic chips by Texas Instruments, namely SN74HC02N, SN74HC04N, SN74HC32N and others. When I connected them in my circuit, the SN74HC02N NOR-gate didn't work as expected, so I searched ...
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2answers
132 views

Flip-Flop Made with 74xx Chips not Latching Consistently

I'm trying to connect two latches made by 74xx chips (normal output: 7404, 7408, 7432...), so that the inverted main output signal is latched into the first circuit on the falling edge and into the ...
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2answers
47 views

Having issues with clocking a 74S374 (D Flip Flop)

I'm having issues setting the state of any of the D Flip Flops, I have jumpers and a multimeter to work with. does the clock pulse have to more precise than touching the jumper to +5v? 74s374J data ...
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2answers
94 views

What is the difference between a 74*374 and a 74*377

What is the exact difference between a 74*374 and a 74*377? The first is classified as an octal edge triggered d-type flipflop while the latter is an 8-bit register. I don't understand the difference ...
0
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1answer
50 views

How to produce five outputs, one low, shifted on clock edge. 74HC logic

I want to produce five outputs, one of which should be low, unless the circuit is in reset, when all should be high. The repeating sequence, on a rising clock edge, should be: ...
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0answers
768 views

4 bit binary full adders, bcd and seven segment displays

I'm having fun with some 74LS283[1] 4 bit binary adders but I am having trouble working out how I should convert the output to a decimal which could be used to drive two 7 segement displays which are ...
3
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1answer
410 views

What 7400-series logic variants include input clamp diodes?

When prototyping, I often use spare 7400-series chips I have lying around. I have a good variety of chips, including many 74HC and 74AHC parts, as well as older varieties like 74LS. From time to time ...
-2
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1answer
492 views

Advantages of 7400 series ICs over diode logic?

I can use diode logic (DRL) or 7400-series logic ICs when I need OR gate or AND gate. Say 74HC08, 74HC11, 74HC21 (AND gates), or 74HC32 (OR gates). Diode logic seems to me simpler, cheaper and thus ...