You are given two circuits as shown in figure, which consists of NAND gates. Identify the logic operation carried out by the two circuits.

(a) Let the output from the 1 st NAND gate will be Y . Therefore, Y = A . B ¯ . A . B ¯ ¯ = A . B ¯ ¯ + A . B ¯ ¯ = A . B + A . B = A . B (b) Let the final output will be Y . Therefore, For the first two gates the output will be A ¯ and B ¯ . So, Y = A ¯ . B ¯ ¯ = A ¯ ¯ + B ¯ ¯ = A + B = A + B The truth table of first circuit is:- A B Y 0 0 0 0 1 0 1 0 0 1 1 1 The truth table of second circuit is:- A B Y 0 0 0 0 1 1 1 0 1 1 1 1

Drawing the circuit diagram, explain the working of p - n junction diode as a full wave rectifier.

Working: The a.c input signal is fed to the primary (P) coil of the transformer. The p-region of both the diodes D1 and D2 are connected to two ends of secondary coil (S). The load resistance (RL) across which output voltage is obtained is connected between common point of n-regions of diodes and central topping of the secondary coil. When positive half cycle of input a.c signal flows through the primary coil, induced emf is set up in the secondary coil due to mutual induction. The direction of induced emf is such that the upper end of secondary coil becomes positive while lower end becomes negative. Thus, D1 diode is forward biased and D2 is reverse biased. So, current through D1 flows through circuit in a direction shown. During negative half cycle of input a.c signal, diode D1 is reverse biased and D2 is forward biased. The current due to D2 flows through circuit in a direction shown. Since, both the halves of input a.c (wave) are rectified, so the junction diode is called Full-wave rectifier. Input and Output waveforms are as shown: