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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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 datasheft happening.
A tristrate output can have 3 different states: Although it is not “best practice” to do this, unconnected LS TTL inputs will usually float high, as PeterBennet has already kindly explained. 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.
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Your explanation “two input are high” sounds more like the definition of an AND gate. Sign up using Facebook.
Post as a guest Name. It is likely that the output remained in a high-impedance state, so the LED did not light.
Email Required, but never shown. And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off.
Then i wired the 19 and 17 pin with 3. 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 have the feeling that I have understood the schematic, but the fact is this is not working. SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour: I don’t use the two G inputs 74ls2441 the same time.
74ks241 have put a led on the 3 output pin, in order to test the output.
74LS 데이터시트(PDF) – Motorola, Inc
Pins 1 and 19 of the LS control this ratasheet for the buffers inside the chip. JvO 2 Therefore it is also no surprise that when you did connect pins 17 and 19 to Vcc, the LED stayed lit.
When you connected [3. And when I connect the Vcc pin [ Note the invertor symbol tiny o ring at the control gate datsaheet to pin 1; you must pull pin 19 high to activate, and pin 1 low to activate. So I clearly don’t understand at all.
(PDF) 74LS241 Datasheet download
This circuit will help: I don’t know that I’d actually seen a chip manufacturer document the behavior, datashest I’ve observed it and understood enough about silicon to understand that two P regions joined by an N region form a transistor.
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. I would have guessed the current gain was more than 0. Mr Bonjour 1 2 Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded? Sign up or log in Sign up using Google.
And if Datashdet 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.
The LED being lit is not a surprise. Do you understand what a buffer is and why we use it? 74ls41
74LS Datasheet PDF –
I didn’t put any resistors on the input. But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected. Note that you may not enable both G inputs e.
And we still don’t know how you have your LED connected???? 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.
MrBonjour Try another gate then.