NOR Gate

• The circuit below has two inputs and one output.
• Whenever at least one of the inputs is high, the corresponding N-type transistor will be closed while the P-type transistor will be open.
• Consequently, the ouput voltage will be low.
• Conversely, if both inputs are low, then both P-type transistors at the top will be closed circuits and the N-type transistors will be open.
• Hence, the output voltage is high.
• The function of this gate can be summarized by the following table:
  

  V1	V2	Output
  Low	Low	High
  Low	High	Low
  High	Low	Low
  High	High	Low

• If logical 1's are associated with high voltages then the function of this gate is called NOR for negated OR.
• Again, there is never a conducting path from the supply voltage to ground.

  

Figure 3.4: NOR Circuit and Standard Symbol