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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MrBonjour Try another gate then. In the first two instances the output is actively pulled low or high using a transistor; in the disconnected state, neither transistor is activated.
74LS 데이터시트(PDF) – Motorola, Inc
This is not unexpected, since you didn’t power the IC via its power pins for this test. Unfortunately your test is datashedt because according to your recent schematic your Vcc supply to the 74LS is only 3.
It is likely that the output remained in a high-impedance state, so the LED did not light. But I thought gate like those didn’t need to be protected.
This circuit will help: If you use a 5V power supply, and dataasheet sure this is always connected to the device Vcc and Gnd pins see belowthen you should see expected behaviour. If you pull pin 19 down, the output will float and both Datashfet will glow dimly because current is passing through both of them.
I didn’t put any resistors on the input. This is clearly what I am expecting.
I don’t use the two G inputs at the same time. Do you have 5 volts Vcc connected to pin 20, datasgeet have pin 10 grounded?
74LS241 Datasheet PDF
When you connected [3. I was expecting that my led will be off with pin 17 not connected but pin dataxheet still high, and the led on with 17 and 19 high, but this is not happening. But my led at pin 18 just glow dimly and never change state, dtaasheet matter if pin 2 is high or not connected. 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.
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74LS Datasheet PDF –
Texas Instruments discusses some of these results of reduced voltage power supply voltages to ICs, in this short ” Designing With Logic ” document. A tristrate output can have 3 different states: And if I’m connecting pin 19 and 17 to be high, I’m expecting datsheet my led will be brighter, but it just glow dimly, no matter if pin 17 is high or not connected. Pins 1 datasheeet 19 of the LS control this state for the buffers inside the chip.
I have put a led on the 3 output pin, in order to test the output.