AND gate
Function
| INPUT | OUTPUT | |
|---|---|---|
| A | B | A AND B |
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
The AND gate is a digital logic gate that behaves according to the truth table to the right. A HIGH output results only if both the inputs to the gate are HIGH. If neither or only one inputs are HIGH, a LOW output results.
Symbols
There are two symbols for AND gates: the 'military' symbol and the 'rectangular' symbol. These are also known as the 'American' and 'British' symbols. For more information see Logic Gate Symbols
Hardware Description and Pinout
AND Gates are basic logic gates, and as such they are recognised in TTL and CMOS ICs. The standard, 4000 series, CMOS IC is the 4081, which includes four independent, two-input, AND gates. The pinout diagram is as follows:
|
|
1 Input A1 2 Input B1 3 Output Q1 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.
As well as the standard 2-Input AND Gate, 3-, 4- and 8-Input AND Gates are also available:
- 4073: Triple 3-Input AND Gate
- 4082: Dual 4-Input AND Gate
- An 8-Input NAND Gate exists (4068), and this is easily made into an 8-Input AND gate by inversion of the output.
Alternatives
If no specific AND gates are available, one can be made from NAND gates in the configuration shown below. Interestingly, any logic gate can be made from a combination of NAND gates
