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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74LS datasheet, Pinout ,application circuits OCTAL BUFFERS AND LINE DRIVERS WITH 3-STATE OUTPUTS

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. I was expecting that my led will be off datahseet pin 17 dtasheet connected but pin 19 still high, and the led on with 17 and 19 high, but this is not happening.

Therefore it is also no surprise that when you did connect pins 17 and 19 to Vcc, the LED stayed lit. I don’t use the two G inputs at the same time.

SE topics where powering devices via other pins, instead of the power pins, 74ls2411 unexpected behaviour: This is clearly what I am expecting. So I clearly don’t understand at all.

But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected. Then [you connected 3. 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. I have tried other gate 19 with 15, 13, 11 and I have the same behavior. Unfortunately your test is invalid because according to your recent schematic your Vcc supply to the 74LS is only 3.


Texas Instruments discusses some of these results of reduced voltage power supply voltages to ICs, in this short ” Designing Datasgeet Logic ” document.

Home Questions Tags Users Unanswered. So here is what I did: And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off. I would have guessed the current gain was more than 74l2s41. In the first two instances the output is actively pulled low or high using a transistor; in the disconnected state, neither transistor is activated. This is not unexpected, since you didn’t power the IC via its power pins for this test.

Note that you may not enable both G inputs e. This will also cause behaviour which is different from the behaviour when correct power is datashdet. 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. Sign up using Facebook. MrBonjour Try another gate then. 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.


I don’t know that I’d actually seen a chip manufacturer 744ls241 the behavior, but I’ve observed it and understood 74sl241 about silicon to understand that two P regions joined by an N region form a transistor.

74LS Datasheet PDF –

Email Required, but never shown. I’m trying to understand how the 74LS works. Why is my microcontroller passing a current through it when not connected? Which I have interpreted as being: I have the feeling that I have understood the schematic, but the fact is this is not working. Without it, the outputs float.

If you pull pin 19 down, the output will float and both LEDs will glow dimly because current is passing through both of 74ls21. Sign up using Email and Password.

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74LS241 Datasheet

Post as a guest Name. Your explanation “two input are high” sounds more like the definition of an AND gate.

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 will cause the datasheett to source current into the adjacent pin. This circuit will help: JvO 2