74LS08 PDF

SN54/74LS QUAD 2-INPUT AND GATE. LOW POWER SCHOTTKY. J SUFFIX . CERAMIC. CASE N SUFFIX. PLASTIC. CASE 1. 1. Symbol. Parameter. DM54LS DM74LS Units. Min. Nom. Max. Min. Nom. Max. VCC. Supply Voltage. 5. 5. V. VIH. High Level Input. Note The ”Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaran- teed The device should not be operated at.

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The two inputs of AND gate are driven out from bases of the two transistors.

74LS08 Quad 2-Input AND Gate Buy Online in India – Robomart

Because output is nothing but voltage across resistor R1 it will be LOW. In this state the current flow through base of both transistors will be zero.

After verifying the 7ls08 states, you can tell that we have satisfied the above truth table. In that case, the left button should have a red wire on the lower left pin. When both buttons are not pressed.

digital logic – 74LS08 AND gate always outputting high? – Electrical Engineering Stack Exchange

Top menu About Us Contact. By using our site, you acknowledge that you have read and 7ls08 our Cookie PolicyPrivacy Policyand our Terms of Service. I think that you were dead on in the first place with your answer SaraHeart. I have tried switching to a 9v battery and nothing changes.

The inputs with both switches unpressed allow the pins to float around, depending on the way the IC is set-up internally. You might be using push buttons that are connected in such a way that the legs are shorted connected together. As you can see the LED is on by default despite neither button being pressed.

Top menu About Us Advertise. And after a google search I havnt come up with anything, usually the videos are terrible quality or they are using a different AND gate. At this time the total VCC appears across resistor R1. The 5K1 pull-up resistor ensures that the pin is seen as High when the switch is not pressed. If you choose the wrong pair, you end up with an always on switch. Sign up using Facebook. The description for each pin is given below.

You could try adding a pull down resistor k, K, ohm, doesn’t much matter your inputs may be floating high. Then if your IC is good your switches are mis-wired, I have done it myself with that type of switch. If you want to absolutely avoid learning the pin out of these push buttons, always connect them in diagonal. Sara Heart 1 6. It is really popular and is available everywhere.

For better understanding the internal working let us consider the simplified internal circuit of AND gate as shown below. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Looking at the image I agree.

There are four legs connected 774ls08 in pair of two.

Pressing the buttons does nothing. The switch between the input pin and Ground will provide a Zero Ohm connection to Ground when the switch is pressed, ensuring that the gate sees the input as a Low.

With that the drop across resistor R1 will be zero. Because total VCC appears across transistors the drop across resistor R1 will be zero.

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The inputs of the 74LS family and other TTL versions source significant current and will appear as a logic High unless firmly pulled to Ground – your k resistors won’t help.

When any one of the buttons 74lss08 pressed. These two inputs are connected to buttons to change the logic of inputs. This LED is connected to detect the state of output. With the LS you need to 74lx08 1. Home Questions Tags Users Unanswered. The chip is available in different packages and is chosen depending on requirement.