Draw a circuit diagram for a two input OR gate and explain its working with the help of input, output waveforms.

 as given in the circuit below: 
 

Working: The negative terminal of the battery is gounded and corresponds to the 0 state and the positive (i.e., voltage 5 V in the present case) to the 1 state. 

Input and output waveform: 



- When both A and B are connected to 0, no current passes through the diode and therefore no voltage develops across R and the output is zero. 

- When input A is connected to zero and B to 1, the diode D₂ is forward biased and the current through it is limited by a current limiting resistance. This current causes a 5 V drop across the resistance assuming the diode to be ideal and this gives an output of 5 V or 1.

- Now, interchanging A and B to 1 and 0 will still give a 5 V drop across the resistance as D₁ will conduct. 

- When the terminals A and B are connected to 1, then both the diodes D₁ and D₂ conduct. However, the voltage drop across R cannot exceed 5 V and the output is 1.