Semiconductor Electronics

Application of a forward bias to a p-n junction

1. widens the depletion zone
2. increases the potential difference across the depletion zone
3. increases the number of donors on the n side
4. decreases the electric field in the depletion zone.

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C, (Eg)Si and (Eg)Ge respectively. Which one of the following relationships is true in their case?

1. (Eg)C > (Eg)Si
2. (Eg)C < (Eg)Si
3. (Eg)C = (Eg)Si
4. (Eg)C < (Eg)Ge.

In a p-n junction photo cell, the value of the photo-electromotive force produced by monochromatic light is proportional to

1. The barrier voltage at the p-n junction.
2. The intensity of the light falling on the cell.
3. The frequency of the light falling on the cell.
4. The voltage applied at the p-n junction.

In semiconductors at room temperature

1. the valence band is partially empty and the conduction band is partially filled
2. the valence band is completely filled and the conduction band is partially filled
3. the valence band is completely filled
4. the conduction band is completely empty

The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The d.c. component of the output voltage is

1. (10/ 2) V
2. ( 10 ) V
3. 10 V
4. (20/ ) V

The output of OR gate is 1

1. if both inputs are zero
2. if either or both inputs are 1
3. only if both inputs are 1
4. if either input is zero

Of the diodes shown in the following diagrams, which one is reverse biased?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Reverse bias applied to a junction diode

1. lowers the potential barrier
2. raises the potential barrier
3. increases the majority carrier current
4. increases the minority carrier current

If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be

1. 25 Hz
2. 50 Hz
3. 70.7 Hz
4. 100 Hz

Barrier potential of a p-n junction diode does not depend on

1. diode design
2. temperature
3. forward bias
4. doping density