![]() ![]() Because output is nothing but voltage across resistor R1 it will be LOW. With that the drop across resistor R1 will be zero. The ON transistor will act as short circuit and OFF transistor acts as open circuit having total VCC appearing across it. Stage2: When any one of the buttons is pressed.In this state the relative transistor will be ON leaving the other OFF. Because total VCC appears across transistors the drop across resistor R1 will be zero. ![]() So the total supply voltage VCC appears across the transistors Q1 and Q2. In this state the current flow through base of both transistors will be zero.Because base current is zeroboth transistors Q1 and Q2 will be OFF. Stage1: When both buttons are not pressed. The circuit working can be explained in few stages below: This LED is connected to detect the state of output. This output is connected to a LED D1 trough a current limiting resistor R2. Output of the AND gate is the voltage across resistor R1. These two inputs are connected to buttons to change the logic of inputs. The two inputs of AND gate are driven out from bases of the two transistors. In the circuit two transistors are connected in series to form a AND gate. For example gate1 performs AND operation between A1 and B1 and provides output at Y1 terminal.įor realizing the above truth table let us take a simple AND gate application circuit as shown below.įor better understanding the internal working let us consider the simplified internal circuit of AND gate as shown below. The four AND gates in the chip mentioned earlier are connected internally as shown in diagram below.Įach AND gate here performs AND operation for two logic inputs. The chip provides TTL outputs which are needed in some systems. It is really popular and is available everywhere.Ĥ. 74LS08 is one of cheapest IC present in market for AND logic operation. Because of this the chip can be used for high speed AND operations.ģ. As mentioned earlier the gates in the chip are designed by SCHOTTKY TRANSISTORS to make the switching delays of gates less. The chip is used in systems where high speed AND operation is needed. There are four AND gates in the chip, we can use one or all gates simultaneously.Ģ. The chip is basically used where AND logic operation is needed. There are many applications of IC 74LS08. SN54LS08, IC 7408, HEF4081, Any two transistors can be reconfigured to form a AND gate. Note: Complete technical details can be found in the 74LS08 Datasheet linked at the bottom of this page.
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