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Circuit Description

This applet demonstrates the static two-input NOR and OR gates in CMOS technology. Click the input switches or type the ('a','b') and ('c','d') bindkeys to control the two gates.

The two-input NOR2 gate shown on the left is built from four transistors. The parallel connection of the two n-channel transistors between GND and the gate-output ensures that the gate-output is driven low (logical 0) when either gate input A or B is high (logical 1). The complementary series-connection of the two transistors between VCC and gate-output means that the gate-output is driven high (logical 1) when both gate inputs are low (logical 0). The net result is the logical NOR function:

  NOR2                   OR2

  A  B  |  Y             A B  |  Z
--------+-----          ------+----
  0  0  |  1             0 0  |  0
  0  1  |  0             0 1  |  1
  1  0  |  0             1 0  |  1
  1  1  |  0             1 1  |  1

As shown on the right, the corresponding OR gate is constructed from the NOR2 followed by a standard static inverter.