NCERT Physics Class 12 Exemplar Ch 14 Semiconductor Electronics Materials Devices and Simple Circuits Part 6

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Q 36 Suppose a ‘n’-type wafer is created by doping Si crystal having with 1ppm concentration of As. On the surface ppm Boron is added to create region in this wafer. Considering , (i) calculate the densities of the charge carriers in the regions. (ii) Comment which charge carriers would contribute largely for the reverse saturation current when diode is reverse biased.

Ans:

In ‘n’ region; number of e– is due to As:

The minority carriers (hole) is

Similarly, when Boron is implanted a ‘p’ type is created with holes

This is far greater than that existed in ‘n’ type wafer on which Boron was diffused.

Therefore, minority carriers in created ‘p’ region

(ii) Thus, when reverse biased , holes of ‘n’ region would contribute more to the reverse saturation current than minority of p type region.

Q 37 An X-OR gate has following truth table:

Title: Table of an X-Or Gate Has Truth Table
A B Y 0 0 0 0 1 1 1 0 1 1 1 0

A

B

Y

0

0

0

0

1

1

1

0

1

1

1

0

It is represented by following logic relation

Build this gate using AND, OR and NOT gates.

Ans:

It is represented by following logic relation

It is Represented by Following Logic Relation

It is represented by following logic relation