# Electronics and Communication Engineering - Electronic Devices and Circuits

1.

Which of these has 3 layers?

 A. PIN diode B. Zener diode C. Schottky diode D. Photo diode

Explanation:

p layer, i layer and n layer.

2.

As per Einstein's equation, the velocity of emitted electron in photoelectric emission is given by the equation

 A. mv2 = hf - Uw B. mv2 ≤ hf - Uw C. mv2 = hf + Uw D. mv2 ≤ hf + Uw

Explanation:

Some electrons have less energy than Fermi level E and, therefore, more energy than Uw to escape.

Therefore, this equation has inequality sign.

3.

For an P-channel enhancement type MOSFET determine the drain current if K = 0.278 x 10-3A/V2, VGS = -4V, VT = -2V, Voltage equivalent at 27°C = 26 mV.

 A. 10 mA B. 1.11 mA C. 0.751 mA D. 46.98 mA

Explanation:

Drain current Id  = k (|Vgs| - |VT|)2

= 0.278 x 10-3(4 - 2)2

= 1.11 mA.

4.

The skin depth of copper is found to be 66 mm at 1 MHz at a certain temperature. At the same temperature and at 2 MHz, the skin depth would be approximately

 A. 47 μm B. 33 μm C. 92 μm D. 1.22 μm

Explanation:

Skin depth = 5.

When p-n junction is reverse biased the holes in p material move towards the junction and electrons in n material move away from the junction.

 A. True B. False