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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A tristrate output can have 3 different states: Note the invertor symbol tiny o ring at the control gate connected to pin 1; you must pull pin 19 high to activate, and pin 1 low to activate. The LED being lit is not a surprise. But I thought gate like those didn’t need to be protected.
Pins 1 and 19 of the LS control this state for the buffers inside the chip. It is not guaranteed to operate at 3. Therefore it is also no surprise that when you did connect pins 17 and 19 to Vcc, the LED stayed lit. Another issue I’ve observed is parts that behave as though pairs of pins are connected via PNP transistor, such that excessive voltage on one datashedt cause the device to source current into the adjacent pin.
Understanding how a tristate buffer works 74LS Ask Question.
74LS 데이터시트(PDF) – Motorola, Inc
MrBonjour Try another gate then. Please show the schematic diagram. Email Required, but never shown. So I clearly don’t understand at all.
(PDF) 74LS241 Datasheet download
Which I have interpreted as: Without it, the outputs float.
Unless you know exactly what you are doing and its consequences, do not apply voltages to the other pins of an IC, without the correct power supply voltage s also being supplied to its specified power pins i. I would have guessed the current gain was more than 0. Then [you connected 3.
Why is my microcontroller passing a current through it when not connected? Home Questions Tags Users Unanswered. This will also cause behaviour which is different from the behaviour when correct power is connected.
Sign up using Facebook. I don’t use the two G inputs at the same time. Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded? I 74la241 put a led on the 3 output pin, in order to test the output.
So here is what I did: What does “put a led on the 3 output pin” mean? Mr Bonjour 1 2 774ls241 If you use a 5V power supply, and make sure this is always datasheeet to the device Vcc and Gnd pins see belowthen you should see expected behaviour.
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. I’m trying to understand how the 74LS works.
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.
So your first tests were done without any power connected to the Vcc pin! When you connected [3. Your explanation “two input are high” sounds more like the definition of an AND gate. And we still don’t know how you have your LED connected????