(a) A student wants to use two p-n junction diodes to convert alternating current into direct current. Draw the labelled circuit diagram she would use and explain how it works.
(b) Give the truth table and circuit symbol for NAND gate.

(a) Full wave rectifier:
 

In positive half cycle of AC, end A becomes positive and D1 becomes forward biased and D2 is reverse biased, so conducts and D2 doesn’t.

So conventional current flows through D1, RL and upper half of secondary winding.

Similarly, during negative half cycle of AC, diode D2 becomes forward biased and D1 is reverse biased, current flows through D2, RL and lower half of secondary winding.

Thus, current flows in same direction in both half cycles of input AC voltage.


(b) The circuit symbol, and the truth table, for the NAND gate, are given below.