|Boolean equation:||y= AB|
|The 7400 consists of 4 (quad) inverted AND gates(Nand) this is the compliment of the output of a regular AND gate. In boolean algebra any Boolean equation can be represented with Nand gates alone.|
It’s a Low-power Schottky family which uses fast Transistor-Transistor Logic (TTL) but requires more power than later families. However later Ic’s are still called TTL even though they do not use TTL anymore. It uses a supply voltage of 5V ï¿½0.25V and should be smoothed with small capacitors in the range of 0.033uF to 0.1uF linked directly over the supply pins as close to the IC as possible to remove power spikes caused by the switching circuits inside the IC itself. all unused pins should be connected to Vcc (+V) to insure that the IC does not pick up ambient noise. The outputof a 74LS can drive up to 10 other 74LS IC inputs but if more inputs need to be driven you should either use a transistor or a BUS-Driver IC. The output can only source +/- 2mA and should use a transistor to drive larger outputs,it can however sink up to 16mA of current and can light a LED which needs 10mA to emit light directly in the inverted state. The time taken to travel through a Gate state is about 10nS and can run at about 25MHz.
uses CMOS logic with the low power consumption of 4000 series IC’s and the high speed of TTL. They have the same pin arrangements as the older 74LS family however the 74HC inputs cannot be driven by 74LS outputs as there low voltage range is not compatible and you should use the 74HCT instead with 74LS compatible inputs. The Inputs have very high impedance and will not affect the circuit they are connected to however this also means that any unconnected input will switch between a high and a low state very rapidly causing an increase in supply current and the ic to behave undesirably. This IC needs a supply voltage of 2 to 6V and is tolerable to voltage spikes. The outputs can both sink and source about 4mA and you should again use either a transistor or a BUS-Driver to switch larger circuits. the output can drive many inputs of 74HC class IC’s quite easily. this IC also has a switching time of about 10nS.
like the 74HC it has high speed TTL and low power consumption of CMOS. The 74HCT can be safely used in the same circuit as 74LS this means it can be used as a direct low power replacements for the older 74LS series. The only problem is that the 74HCT has a lower immunity to noise, but this usually is not a problem in most systems. The Ic needs a supply of 4.5V to 5.5V so its best to use a smoothing circuit for the supply voltage. both the 74HC and 74HCT series IC’s are static sensitive. Touching a pin while your body holds a charge can damage the IC. most common IC’s are quite tolerant but it is advisable to discharge yourself with an anti-static wrist strap connected to earth or ground yourself quite regally by touching something metal that is earthed before handling them. ICs should be stored in protective packaging until you are ready to use them. if you are designing a new circuit you should use the 74HC family.
List of other NAND gates:
74134: 12-Input NAND gate with Three-state Output
7413: Dual Schmitt trigger 4-input NAND gate
7420: Dual 4-input NAND gate
7422: Dual 4-Input NAND gate with open collector outputs
7440: Dual 4-input NAND Buffer
74140: Dual 4-input NAND Line Driver
7410: Triple 3-input NAND gate
7412: Triple 3-input NAND gate with open collector outputs
7400 Quad 2-input NAND gate
7401 Quad 2-input NAND gate with open collector outputs
7403: Quad 2-input NAND gate with open collector outputs (different pinout than 7401)
7424: Quad 2-input NAND gate gates with schmitt-trigger line-receiver inputs.
7426: Quad 2-input NAND gate with 15V open collector outputs
7437: Quad 2-input NAND Buffer
7438: Quad 2-input NAND Buffer with open collector outputs
7439 Quad 2-input NAND Buffer
74132: Quad 2-input NAND Schmitt trigger
74804: Hex 2-input NAND Drivers
4011 – Buffered Quad 2-Input NAND gate
4012 – Dual 4-input NAND gate
4023 – Triple 3-input NAND
4044 – Quad NAND R/S ((tristate) outputs)
4068 – 8-input NAND gate
4093 – Quad 2-input Schmitt trigger NAND gate
4572 – Hex gate : quad NOT, single NAND, single NOR
40107 – dual 2-input NAND buffer/driver