Practical Electronics/IC/4081

CMOS 4081 Quad 2-Input AND Gate 14 7408 0 0 0 1 The 4081 is a member of the 4000 Series CMOS range, and contains four independent CMOS AND gates, each with two inputs. The pinout diagram, given on the right, is the standard two-input logic gate IC layout: Pin 7 is the negative supply Pin 14 is the positive supply Pins 1&2, 5&6, 8&9, 12&13 are gate inputs Pins 3, 4, 10, 11 are gate outputs The truth table for one of the four gates is shown to the right. For more information about the AND gate in general, see this module. The arrangement of the CMOS components is shown below: center|375px This chip is widely available, and usually comes in a DIL-14 or SOIC-14 package. This chip is different in pinout to the TTL 7408 and 7409, but can fulfill the function of either if the wiring is modified. Alternative Construction If a 4081 is not available, there are several ways to achieve an AND gate. The first is to use a NAND gate and invert the output. This can be done with a NOT gate or another NAND gate. The first method with require two ICs to implement, but a total of four gates can be made. The second will require only one IC, but only two gates can be made. Incidentally, due to the nature of CMOS devices, this gate actually produces the AND function by inverting the output of a NAND gate (see above). center|240px center|240px NOR gates can also be used in the configuration below to make an AND gate. center|240px Similar ICs 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. Some models of this IC have an onboard NOT gate or an inverted output for this purpose. AND gates with more inputs can be made up from the 4081 or any of the above ICs by cascading them together. This is discussed on this page. Datasheets These are available from manufacturers. A selection of different manufacturers' datasheets is given below: Philips Semiconductor Fairchild Semiconductor ON Semiconductor Texas Instruments