74LS08 IC is a member of 74XXYY IC series. There are four AND gates in the chip and each gate have two inputs, hence the name. 74LS SN74LS08NSR. ACTIVE. SO. NS. Green (RoHS. & no Sb/Br). CU NIPDAU. LevelC-UNLIM. 0 to 74LS SN74S08D. ACTIVE. 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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Both transistors will be ON and voltage across both of them will be zero.

Sign up using Email and Password. It is really popular and is available everywhere. These two inputs are connected to buttons to change the logic of inputs.

Something similar should be done to the right button.

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74LS08 Quadruple 2 Input Positive AND Gate IC

Because of this the chip can be used for high speed AND operations. Email Required, but never shown. If you want to absolutely avoid learning the pin out of these push buttons, always connect them in diagonal. The chip is available in different packages and is chosen depending on requirement. In that case, the left button should have a red wire on the lower left pin. It might be oscillating as well. Pressing the buttons does nothing.


The inputs of the 74LS family 74le08 other TTL versions source significant current and will appear as a logic High unless firmly pulled to Ground – your k resistors anf help. I am new to electrical engineering still so forgive me if I am making a stupid mistake. I think that you were dead on in the first place with your answer SaraHeart.

You might be using push buttons that are connected in such a way that the legs are shorted connected together.

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. It is currently powered by a 5v 1. Pull down resistors as suggested in another answermight also a good idea.

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As you can see the LED is on by default despite neither button being pressed. When any one of the buttons is pressed. The circuit working can be explained in few stages below: You could try adding a pull down 74ls088 k, K, ohm, doesn’t much matter your inputs may be floating high. The chip is used in systems where high speed AND operation is needed.


TL — Programmable Reference Voltage. Because total VCC appears across transistors the drop across resistor R1 will be zero. When both znd are not pressed.

For better understanding the internal working let us consider the simplified internal circuit of AND gate as shown below. The two inputs of AND gate are driven out from bases of the two transistors. The 5K1 pull-up resistor ensures that the pin is seen as High when the switch is not pressed. Sign up using Facebook. The description for each pin is given below.

The inputs on CMOS parts anything with a “C” in the middle source or sink very little current, so K pull-up or -down will work with them.