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Circuit Description

This applet shows a typical so-called CMOS complex gate, the and-or-invert AOI22.

Click the input switches or type the ('a','b','c','d') bindkeys to control the circuit.

A complex or compound gate makes use of the typical structure of static CMOS gates to efficiently realize certain logical functions. The most common complex gates are used to implement the and-or-invert and or-and-invert (see next applet) functions. The gate shown here requires just eight transistors to implement the logical function

  Y = NOT( (A & B) | (C & D))

Correspondingly, the n-channel transistors controlled by A and B are connected in series, as are the transistors controlled by C and D. Both pairs of transistors are then connected in parallel to realize the lower part of the gate. The complementary structure of p-channel transistors consists of the series-connection of two pairs of parallel connected transistors.

  A B C D  |  Y
 ----------+----
  0 0 0 0  |  1
  0 0 0 1  |  1
  0 0 1 0  |  1
  0 0 1 1  |  0
  0 1 0 0  |  1
  0 1 0 1  |  1
  0 1 1 0  |  1
  0 1 1 1  |  0
           |
  1 0 0 0  |  1
  1 0 0 1  |  1
  1 0 1 0  |  1
  1 0 1 1  |  0
  1 1 0 0  |  0
  1 1 0 1  |  0
  1 1 1 0  |  0
  1 1 1 1  |  0