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 have tried other gate 19 with 15, 13, 11 and I have the same behavior. Which I have interpreted as: If you pull pin 19 down, the output will float and both LEDs will glow dimly because current is passing through both of them.
From what I read, if two input are high on a buffer, then the output will be high.
Without it, the outputs float. SE topics where powering datasbeet via other pins, instead of the power pins, caused unexpected behaviour: I have the feeling that I have understood the schematic, but the fact is this is not working.
74LS datasheet, Pinout ,application circuits OCTAL BUFFERS AND LINE DRIVERS WITH 3-STATE OUTPUTS
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. This is clearly what I am expecting. Pins 1 and 19 of the LS control this state for the buffers inside the chip. datasheer
Note that you may not enable both G inputs e. 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.
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. But I thought 74os241 like those didn’t need to be protected. Although it is not “best practice” to do this, unconnected LS TTL inputs will usually float high, as PeterBennet has already kindly explained.
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SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour:. Texas Instruments discusses some of these results of reduced voltage power supply voltages to ICs, in this short ” Designing With Logic ” document.
OCTAL BUFFERS AND LINE DRIVERS WITH 3-STATE OUTPUTS
And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off. And we still don’t know how you have your LED connected????
Therefore any results you get using a power supply of 3.
Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded? This is not unexpected, since you didn’t power the IC via its power pins for this test. But my led at pin 18 just glow dimly and never change state, no matter if pin 2 is high or not connected.
74LS 데이터시트(PDF) – Motorola, Inc
The LED being lit is not a surprise. Sign up using Facebook.
Email Required, but never shown. Mr Bonjour 1 2 It is not guaranteed to operate at 3.