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Draw an OR gate using two diode and explain its operation. Write the truth table and logic symbol of OR gate. |
Answer» Solution :OR Gate `:` It has two input terminals and one output terminal.If both inputs are low the output is low. If one of the inputs is high, or both the inputs are high then the output of thegate is high.The truth tables of OR gate. In truth table logicfunction is written as A or B 'OR' logic function is represented by the symbol 'plus' `Q = A+B ` Logic gate 'OR' is shown given below . Implementation of OR gate using diode `:` Let `D_(1)` and `D_(2)` be two DIODES. A potential of 5V represents the logical value 1 A potential of 0V REPRESENTES the logicalvalue 0. When A=,B=0 both the diodes are reverse BIASED and there is no current through the resistance .So, the potential at Q is zero i.e., Q = 0 . When A=0 or B =0 and the other equal to a potential of 5Vthe diode whose anode is at a potential of 5V is forward-biasedand that diode behaves like a closed switch. The output potential then becomes5V i.e., Q =1.When both A and B are 1, both the diodes are forward -biased and the potential at Q is same as that at A and Bwhcih is 5V i.e., Q =1 . The output is same as that of the OR gate.  
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