Logical Electronic

Special Output Gates

It is sometimes desirable to have a logic gate that provides both inverted and non-inverted outputs.
For example, a single-input gate that is both a buffer and an inverter, with a separate output terminal
for each function.

Or, a two-input gate that provides both the AND and the NAND functions in a single circuit. Such gates do exist and they are referred to as complementary output gates. The general symbology for such a gate is the basic gate figure with a bar and two output lines protruding from it. An array of complementary gate symbols is shown in the following illustration:

Special output gates

Complementary gates are especially useful in "crowded" circuits where there may not be enough
physical room to mount the additional integrated circuit chips necessary to provide both inverted
and noninverted outputs using standard gates and additional inverters.

They are also useful in applications where a complementary output is necessary from a gate, but the addition of an inverter would introduce an unwanted time lag in the inverted output relative to the noninverted output.


The internal circuitry of complemented gates is such that both inverted and noninverted outputs
change state at almost exactly the same time:



Keywords : 4066, CMOS Bilateral, Switch, Gate, Cmos, Gates, CMOS-gates, Logic Gate, Complementary, AND, OR, XOR, Gates
Writer : delon  |
26 Nov 2006 Mon   
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