## Thursday, 6 June 2013

### Video Solutions for GATE 2005 ECE : Two Mark Questions (Electron Devices)

1.  A silicon sample A is doped with 1018 atoms / cm3 of boron.

Another sample B of identical dimensions is doped with 1018

atoms /cm3 of phosphorous. The ratio of electron to hole

mobility is 3. The ratio of conductivity of the sample A to B is

2.  A silicon PN junction diode under reverse bias has depletion

region of width 10µm. the relative permittivity of silicon Ɛr is

11.7 and the permittivity of free space Ɛo = 8.85x10-12 F/m. the

depletion capacitance of the diode per square meter is

3.  For an npn transistor connected as shown in figure,

VBE = 0.7 volts. Given that reverse saturation current of the

junction at room temperature 300oK is 10-13 Amp, the emitter

current is

4.  For an n-channel MOSFET and its transfer curve shown in

figure, the threshold voltage is

5. The zener diode in the regulator circuit shown in figure has a

zener voltage of 5.8 volts and a zener knee current of 0.5 mA.

The maximum load current drawn from this circuit ensuring

proper functioning over the input voltage range between 20

and 30 volts is

6. Both transistors T1 and T2 in figure have a threshold voltage of

1 volt. The device parameters k1 and k2 of T1 and T2 are ,

36 µA/V2 and 9 µA/V2 , respectively. The output voltage Vo is

7. A MOS capacitor made using p type substrate is in the

accumulation mode. The dominant charge in the channel

is due to the presence of