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. µA. VCC = MAX, VIN = V. IIH. In ut HIGH Current. mA. VCC = MAX, VIN = V. IIL. Input LOW Current. – mA. VCC = MAX, VIN = V. IOS. 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.
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The chip is available in different packages and is chosen depending on requirement. The description for each pin is given below.
The chip is basically used where AND logic operation is needed. There are four AND gates in the chip, we can use one or all gates simultaneously. The chip 74ls088 used in systems where high speed AND operation is needed. Because of this the chip can be used for high speed AND operations.
It is really popular and is available everywhere. The four AND gates in the chip mentioned earlier are connected internally as shown in diagram below.
For realizing the above truth table let us take a simple AND gate application circuit as shown below. For better understanding the internal working let us consider the simplified internal circuit of AND gate as shown below.
In the circuit two transistors are connected in series to form a AND gate. The two inputs of AND gate are driven out from bases of the two transistors. These two inputs are connected to buttons to change the logic of inputs. Output of the AND gate is 74ks08 voltage across resistor R1.
This LED is connected to detect the state of output. When both buttons are not pressed.
74LS08 – Quad 2-In AND Gate
In this state the current flow through base of both transistors will be zero. Because total VCC appears across transistors the drop across resistor R1 will be zero. Because output is nothing but voltage across resistor R1 it will be LOW.
When any one of the buttons is pressed. With that the drop 74os08 resistor R1 will be zero. When both buttons are pressed. Both transistors will be ON and voltage across both of them will be zero. At this time the total VCC appears across resistor R1. After verifying the three states, you can tell that we have satisfied the above truth table. Submitted by admin on 6 April A few mentioned below. The chip provides TTL outputs which are needed in some systems.
The circuit working can be explained in few stages below: TL — Programmable Reference Voltage.