Semiconductor Electronics: Materials, Devices and Simple Circuits Test 2

$$x$$	$$y$$	$$\overline{x}$$	$$a=x.y$$	$$b=\overline{x}.y$$	$$z=\overline{a.b}$$
0	0	1	0	0	1
0	1	1	0	1	1
1	0	0	0	0	1
1	1	0	1	0	1

To get final output as 1, the output of OR gate must be 1 and C must be 1.
So, a = 1, b =0 or a=0, b=1.

the current through 500 ohm resistor is 0.01 ampere as voltage across is 5V.

Since, when A and B both are logic 1 then no current will flow through the both  $$50\Omega$$
resistors, because both the diodes will not conduct. therefore, whole current will flow through $$R=10K$$
and output is potential difference across the $$R=10K$$ which will be $$6 V$$ in this case means high 
Now, When either of the input is low current through terminal which is low will flow through it and most of the current will flow through the $$50\Omega$$ resistance since it is very very less than $$R=10K$$ therefore, Potential across $$R=10K$$ will be less than $$1 V$$ . Hence, when either of input is low output is also low.
When both the inputs are low same case as when either of input is low will be there hence output will also be low.
Therefore, above circuit acts as a AND Logic gate.

In p-type materials holes are majority carriers and electrons are majority carriers in n-type materials. When the two types of semiconductor materials are joined together, the electrons from the n-type material diffuse into p-type material and combines with holes as their concentration is higher in n-type layer. This creates a layer of negative ions near the junction in p-type material. Negative ions are formed because the trivalent impurities (e.g., Aluminum) now has an extra electron from the n-type material. Similarly, the holes from the p-type material diffuse into n-type material resulting in a layer of positive ions in the n-type material.
These negative ions creates an electric field in the direction from n-type to p-type. As more electrons diffuse into p-type material, the electric field strength goes on increasing. The electrons from n-type material now diffusing into p-type material will have to overcome the electric field due to negative ions. At one point, the electric field becomes sufficiently strong to stop further diffusion of electrons. 

Here the logic gates used are OR gate, AND gate. So, if we input values $$0$$ and $$1$$ to the OR gate, the output will be $$1$$. This output along with another input $$1$$ will be used as input for the AND gate. Thus, the final output is $$1$$.

It is clear from given logic circuit, that output Y is low when both the inputs are high, otherwise it is high. Thus, logic circuit is NAND gate.

A	B	Y
1	1	0
0	0	1
0	1	1
1	0	1

From left side the first gate is OR gate and next one is AND gate. So the out put of OR gate  is $$A+B$$ and the output of AND gate $$Y=(A+B).C$$

A B Y
0  0 0
0  1  0
1  0  0
1   1   1
AND gate.