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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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. 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 device to source current into the adjacent pin.

I would have guessed the current gain was more than 0. Unfortunately your test is invalid because according to your recent schematic your Vcc supply to the 74LS is only 3. I don’t use the two G inputs at the same time. Mr Bonjour 1 2 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.

(PDF) 74LS241 Datasheet download

This is not unexpected, since you didn’t power the IC via its power pins for this test. Post as a guest Name. The LED being lit is datxsheet a surprise.

But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected. Email Required, but never shown. Daatsheet 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. 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.


Do you understand what a buffer is and why we use it?

I was wondering if I didn’t have broke datasgeet chip because I don’t have protected the input gate, but it wasn’t asked in the schema. Your explanation “two input are high” sounds more like the definition of an AND gate. A tristrate output can have 3 different states: Sign up or log in Sign up using Google.

So here is what I did: From what I read, if two input are high on a buffer, then the output will be high. Understanding how a tristate buffer works 74LS Ask Question. And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off.

Although it is not “best practice” to do this, unconnected LS TTL inputs will usually 74le241 high, as PeterBennet has already kindly explained. SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour: This circuit will help: Which I have interpreted as: In the first two instances the output is actively pulled 74l2s41 or high using a transistor; in the disconnected state, neither transistor is activated.

But I thought gate like those didn’t need to be protected. Which I have interpreted as being: Without it, the outputs float. MrBonjour Try another gate then. If you use a 5V power supply, and make sure this datqsheet always connected to the device Vcc and Gnd pins see belowthen you should see expected behaviour. I’m trying to understand how the 74LS works.

Therefore any results you get using a power supply of 3. 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 didn’t put any resistors on the input. I have tried other gate 19 with 15, 13, 11 and I have the same behavior. Please show the schematic diagram. Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded? 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.



Do you understand WHY we have tri-state outputs? Note that you may not enable both G inputs e. Why is my microcontroller passing a current through it when not connected? JvO 2 And we still don’t know how you have your LED connected???? Dataheet is likely that the output remained in a high-impedance state, so the LED did not light.

74LS Datasheet PDF –

This is clearly what I am expecting. I have the feeling that I have understood the schematic, but the fact is dataheet is not working. 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. 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.

Therefore it is also no surprise that when you did connect pins 17 and 19 to Vcc, the LED stayed lit. So your 74ls2441 tests were done without any power connected to the Vcc pin!

I have put a led on the 3 datasgeet pin, in order to test the output. Note the invertor symbol tiny o ring at the control gate connected to pin catasheet you must pull pin 19 high to activate, and pin 1 low to activate.