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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Note that you may not enable both G inputs e. I would have guessed the current gain was more than 0. And when I connect the Vcc pin, without 19 and 17, my led is on, where I expected this to be off.
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. 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.
And we still don’t know how you have your LED connected????
74LS datasheet, Pinout ,application circuits OCTAL BUFFERS AND LINE DRIVERS WITH 3-STATE OUTPUTS
Without it, the outputs float. 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. Do you have 5 volts Vcc connected to pin 20, and have pin 10 grounded? Home Questions Tags Users Unanswered.
This is 74ls2241 what I am expecting. I have put a led on the 3 output pin, in order to test the output. JvO 2 Do datsheet understand WHY we have tri-state outputs? SE topics where powering devices via other pins, instead of the power pins, caused unexpected behaviour:. 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. Pins 1 and 19 of the LS control this state for the buffers inside the chip. So here is what I did: But I thought gate like those didn’t need to vatasheet protected.
Unfortunately your test is invalid because according to your recent schematic your Vcc supply to the 74LS is only 3. But my led at pin 18 just glow dimly and never xatasheet state, no matter if pin 2 is high or not connected. Email Required, but never shown. I didn’t put any resistors on the input.
A tristrate output can have 3 different states: Then [you connected 3. So I clearly don’t understand at all. Note the invertor symbol tiny o ring at the control gate connected to datasbeet 1; you must pull pin 19 high to activate, and pin 1 low to activate. I have tried other gate 19 with 15, 13, 11 and I have the same behavior.
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. 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.
74LS 데이터시트(PDF) – Motorola, Inc
So your first tests were done without any power connected to the Vcc pin! When you connected [3. Please show the schematic diagram. The Datsheet being lit is not a surprise. 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.
It is not guaranteed to operate at 3. It is likely that the output remained in a high-impedance state, so the LED did not light.