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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JvO 2 It is likely that the output remained in a high-impedance state, so the LED did not light.

So here is what I did: And when I connect the Vcc pin [ SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour:. SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour: Therefore any results you get using a power supply of 3.

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. 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.

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. Pins 1 and 19 of the LS control this state for the buffers inside the chip. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.


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.

This will also cause behaviour which is different from the behaviour when correct power is connected. I don’t use the two G inputs at the same time.

A 74LS or any 74LS family part will normally see an unconnected dataseet as a High – you need to connect inputs directly to Ground to input a Low. In the first two instances the output is actively pulled low or high using a transistor; in the disconnected state, neither transistor is activated.

When you connected [3. And we still don’t know how you have your LED connected????

Which I have interpreted as being: 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. What does “put a led on the 3 output pin” mean? I have tried other gate 19 with 15, 13, 11 and I have the same behavior. Understanding how a tristate buffer works 74LS Ask Question. I was wondering if I didn’t have broke my chip because I don’t have protected the input gate, but it wasn’t asked in the schema.

I have put a led on the 3 output pin, in order to test the output.

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

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  ASTM F1267 PDF

For some reason, this isn’t working on my circuit.

Why is my microcontroller passing a current through it when not connected? Do you understand WHY we have tri-state outputs? A tristrate output can have 3 different states: If you pull pin 19 down, the output will float and both LEDs will glow dimly because current is passing through both of them. 74l241 you understand what a buffer is and why we use it? Post as a guest Name. Mr Bonjour 1 2 So I clearly don’t understand at all.

74LS241 Datasheet PDF

From what I read, if two input are high on a buffer, then 74lls241 output will be high. It is not guaranteed to operate at 3. This is not unexpected, since you didn’t power the IC via its power pins for this test. I would have guessed the current gain was more than 0.

The LED being lit is not a surprise. MrBonjour Try another gate then.

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

Do you have 5 volts Vcc connected datashet pin 20, and have pin 10 grounded? Sign up using Facebook. I have the feeling that I have understood the schematic, but the fact is this 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.