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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But I thought gate like those didn’t need to be protected.
74LS241 Datasheet PDF
It is likely that the output remained in a high-impedance state, so the LED did not light. 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 74s241 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. Home Datashdet Tags Users Unanswered. When you connected [3.
And we still don’t know how you have your LED connected???? But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected. So I clearly don’t understand at all.
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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. Which I have interpreted as: Your explanation “two input are high” sounds more like the definition of an AND gate. And when I connect the Vcc pin [ Texas Instruments discusses some of these results of reduced voltage power supply voltages to ICs, in this short ” Designing With Logic ” document.
JvO 2 daatasheet If you pull pin 19 down, the output will float and both LEDs will glow dimly darasheet current is passing through both of them.
I would have guessed the current gain was more than 0. I’m trying to understand how the 74LS works. Without it, the outputs float. So here is what I did: Which I have interpreted as being: Do you understand WHY we have tri-state outputs? Please show the schematic diagram. So your first tests were done without any power connected to 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. Understanding how datasgeet tristate buffer works 74LS Ask Question.
Therefore any results you get using a power supply of 3. Email Required, but never shown. Note that you may not enable both G inputs e. 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. This is not unexpected, since you didn’t power the IC via its power pins for this test.
Sign up using Facebook. And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off. 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. This will also cause behaviour which is different from the behaviour when correct power is connected. Then [you connected 3. It is not guaranteed to operate at 3. I was expecting that my led will be off with pin 17 not connected but pin 19 still high, and ddatasheet led on with 17 74ks241 19 high, but this is not happening.
74LS datasheet, Pinout ,application circuits OCTAL BUFFERS AND LINE DRIVERS WITH 3-STATE OUTPUTS
Pins 1 and 19 of the LS control this state for the buffers inside the chip. For some reason, this isn’t working on my circuit. Post as a guest Name. 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. If you use a 5V power supply, and make sure this is always connected to the device 74os241 and Gnd pins see belowthen you should see expected behaviour. Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded?
I didn’t put any resistors on the input. From what I read, if two input are high on a buffer, then the output will be high. In the first two instances the output is actively pulled low or high using a transistor; in the disconnected state, neither transistor is activated. Then i wired the 19 and 17 pin with 3.
Do you understand what a buffer is and why we use it? SE topics datashedt powering devices via other pins, instead of the power pins, caused unexpected behaviour: Although it is not “best practice” to do this, unconnected LS TTL inputs will usually float high, as PeterBennet has already kindly explained.