Semiconductor Electronics

A potential divider circuit is connected with a dc source of 20 V, a light emitting diode of glow in voltage 1.8 V and a zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is cm. [figure]

The correct truth table for the following logic circuit is : [figure]

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

The acceptor level of a p-type semiconductor is 6 eV. The maximum wavelength of light which can create a hole would be : Given hc = 1242 eV nm.

1. 407 nm
2. 103.5 nm
3. 414 nm
4. 207 nm

Following gates section is connected in a complete suitable circuit. [figure] For which of the following combination, bulb will glow (ON) :

1. A = 1, B = 1, C = 1, D = 0
2. A = 1, B = 0, C = 0, D = 0
3. A = 0, B = 0, C = 0, D = 1
4. A = 0, B = 1, C = 1, D = 1

The output (Y) of logic circuit given below is 0 only when : [figure]

1. A = 0, B = 0
2. A = 0, B = 1
3. A = 1, B = 0
4. A = 1, B = 1

The value of net resistance of the network as shown in the given figure is : [figure]

1. ( 3011 )
2. 6
3. ( 52 )
4. ( 154 )

Which of the diode circuits shows correct biasing used for the measurement of dynamic resistance of p-n junction diode :

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

Identify the logic gate given in the circuit : [figure]

1. OR gate
2. NAND gate
3. NOR gate
4. AND gate

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance Rs to regulate the input unregulated supply is : [figure]

1. 10 k
2. 10
3. 1 k
4. 37 k < Rs < 35 k

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be ( X8 )eV. The value of X is : (Given, h=6.6 10-34 Js, e=1.6 10-19 C)

1. 11
2. 13
3. 15
4. 21