The 74HC266N CMOS integrated circuit contains 4 XNOR logic gates, which is the negated form of the XOR gate, it is generally more used to perform flip flops, which is one of the main functions of this gate.
Wide Operating Voltage Range of 2 V to 6 V
High-Current Inverting Outputs Drive Up To10 LSTTL Loads
Low Power Consumption, 20-µA Max ICC
Typical TDP = 10 ns
±4-mA Output Drive at 5 V
Low Input Current of 1 µA Max
Logic Gate XNOR 74HC266N Pinout:
the “Exclusive-NOR” gate is a combination of the Exclusive-OR gate and the NOT gate but has a truth table similar to the standard NOR gate in that it has an output that is normally at logic level “1” and goes “LOW” to a logic level “0” when ANY of its inputs are at logic level “1”.
However, an output “1” is only obtained if BOTH of its inputs are at the same logic level, either binary “1” or “0”. For example, “00” or “11”. This input combination would then give us the Boolean expression of Q = (A ⊕ B) = A.B + A.B
Then the output of a digital logic Exclusive-NOR gate ONLY goes “HIGH” when its two input terminals, A and B are at the “SAME” logic level which can be either at a logic level “1” or at a logic level “0”. In other words, an even number of logic “1’s” on its inputs gives a logic “1” at the output, otherwise is at logic level “0”.
Then this type of gate gives an output “1” when its inputs are “logically equal” or “equivalent” to each other, which is why an Exclusive-NOR gate is sometimes called an Equivalence Gate.
The logic symbol for an Exclusive-NOR gate is simply an Exclusive-OR gate with a circle or “inversion bubble”, ( ο ) at its output to represent the NOT function. Then the Logic Exclusive-NOR Gate is the reverse or “Complementary” form of the Exclusive-OR gate, (A ⊕ B) we have seen previously.
The Exclusive-NOR Gate, also written as “Ex-NOR” or “XNOR”, a function is achieved by combining standard gates together to form more complex gate functions and an example of a 2-input Exclusive-NOR gate is given below.
2-input Ex-NOR Gate
|Boolean Expression Q = A ⊕ B||Read if A AND B the SAME
Giving the Boolean expression of Q = AB + AB
The logic function implemented by a 2-input Ex-NOR gate is given as “when both A AND B are the SAME” will give an output at Q. In general, an Exclusive-NOR gate will give an output value of logic “1” ONLY when there is an EVEN number of 1’s on the inputs to the gate (the inverse of the Ex-OR gate) except when all its inputs are “LOW”.