XNOR gate
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- This article is about XNOR in the sense of an electronic logic gate. For XNOR in the purely logical sense, see Logical equality. For logic gates generally, see Logic Gate.
Function
| INPUT | OUTPUT | |
|---|---|---|
| A | B | A XNOR B |
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
The XNOR gate is a digital logic gate that behaves according to the truth table to the right. A HIGH output results if both of the inputs to the gate are the same. If one but not both inputs are HIGH, a LOW output results.
Symbols
There are two symbols for XNOR gates: the 'military' symbol and the 'rectangular' symbol. For more information see Logic Gate Symbols
Hardware description and pinout
XNOR Gates are basic logic gates, and as such they are recognised in TTL and CMOS ICs. The standard, 4000 series, CMOS IC is the 4077, which includes four independent, two-input, XNOR gates. The pinout diagram is as follows:
|
1 Input A1 2 Input B1 3 Output 4Q1 4 Output Q2 5 Input B2 6 Input A2 7 Vss 8 Input A3 9 Input B3 10 Output Q3 11 Output Q4 12 Input B4 13 Input A4 14 Vdd |
This device is available from most semiconductor manufacturers such as Philips. It is usually available in both through-hole DIL and SOIC format. Datasheets are readily avaialble in most Datasheet Databases.
Alternatives
If no specific XNOR gates are available, one can be made from five NAND gates in the configuration shown below. Interestingly, any logic gate can be made from combinations of NAND gates
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