SN54/74LS • SN54/74LS • SN54/74LS DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified). S. b l. P. 74LS Octal Buffers AND LINE Drivers WITH 3-state Outputs SN74S, SN74S OCTAL BUFFERS Details, datasheet, quote on part number: 74LS Texas Instruments 74LS Buffers & Line Drivers are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for Texas Instruments .

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Sign up using Email and Password. Texas Instruments discusses some of these results of reduced voltage power supply voltages to ICs, in this short ” Designing Catasheet Logic ” document. So here is what I did: I didn’t put any resistors on the input. Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded?

74LS241 Datasheet PDF

I would have guessed the current gain was more than 0. I don’t know that I’d actually seen a chip manufacturer document the behavior, but I’ve observed it and understood enough about silicon to understand that two P regions joined by an N region form a transistor.

I’ve done quite a lot of research since first writing this answer, and with unpowered 74LS devices and an input voltage between 0 V and 5.

MrBonjour Try another gate then. But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected.


74LS Datasheet(PDF) – National Semiconductor (TI)

Pull pin 19 high, and the output will follow the input 17 and either the green or the red LED will glow brightly; the other one will be off.

I was expecting that my led will be off with pin 17 not connected but pin 19 still high, and the led on with 17 and 19 high, but this is not happening. Then i wired the 19 and 17 pin with 3. It is likely that the output remained in a high-impedance state, so the LED did not light.

Do you understand what a buffer is and why we use it? And when I connect the Vcc pin [ A 74LS or any 74LS family part will normally see an unconnected input as a High – you need to connect inputs directly to Ground to input a Low.

I have the feeling that I have understood the schematic, but the fact is this is not working. Then [you connected 3. It is not guaranteed to operate at 3. Home Questions Tags Users Unanswered. Email Required, but never shown. For some reason, this isn’t working on my circuit.

Which I have interpreted as: Note the invertor symbol tiny o ring at the control gate connected to pin 1; you datasheer pull pin 19 high to activate, and pin 1 low to activate. Your explanation “two input are high” sounds more like the definition of an AND gate.


This is clearly what I am expecting. What does “put a led on the 3 output pin” mean? If you use a 5V power supply, and make sure this is always connected to the device Vcc and Gnd pins see belowthen you should see expected behaviour.

Which I have interpreted as being: So I clearly don’t understand at all. Why is my vatasheet passing a current through it when not connected? This will also cause behaviour which is different from the behaviour when correct power is connected.

When you connected [3. I’m trying to understand how the 74LS works.

(PDF) 74LS241 Datasheet download

These ‘G’ inputs must be activated in order to have the buffers connected to them pull their outputs low or high, depeding on their input. And if I’m connecting pin 19 and 17 to be high, I’m expecting that my led will be brighter, but it just glow dimly, no matter if pin 17 is high or not connected. Do you understand WHY we have tri-state outputs?

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