TRANSISTOR AS A NAND GATE

NAND gate is the universal gate which can be used to design any boolean expression. the symbol of NAND gate is shown in figure 1. any gate can be derived from the NAND gate that's why NAND gate is called universal gate.

truth table of nand gate is

we can make nand gate by using transistor as a switch.The circuit diagram of the practical circuit of transistor as a not gate is shown below. three images shows the state of led when switches are pressed one by one