Pure \(Si\) at \(500\) K has equal number of electron \((n_i)\) and hole \((n_h)\) concentration of \(1.5\times10^{16}~\text{m}^{-3}.\) Doping by indium increases \(n_h\) to \(4.5\times 10^{22}~\text{m}^{-3}\). The doped semiconductor is of:
1. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=5\times10^{22}~\text{m}^{-3}\)
2. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=2.5\times10^{23}~\text{m}^{-3}\)
3. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=2.5\times10^{10}~\text{m}^{-3}\)
4. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=5\times10^{9}~\text{m}^{-3}\)

Subtopic:  Types of Semiconductors |
 69%
From NCERT
NEET - 2011
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A Zener diode, having breakdown voltage equal to \(15\) V, is used in a voltage regulator circuit, as shown in the figure. The current through the diode is:

                      
1. \(10\) mA
2. \(15\) mA
3. \(20\) mA
4. \(5\) mA

Subtopic:  Applications of PN junction |
 60%
From NCERT
NEET - 2011
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Which one of the following statement is false?

(1) Pure Si doped with trivalent impurities gives a p-type semiconductor 

(2) Majority carries in a n-type semiconductor are holes

(3) Minority carries in a p-type semiconductor are electrons

(4) The resistance of intrinsic semiconductor decreases with increase of temperature 

Subtopic:  Types of Semiconductors |
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From NCERT
NEET - 2010
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The device that can act as a complete electronic circuit is

1. Junction diode

2. Integrated circuit

3. Junction transistor

4. Zener diode

Subtopic:  Transistor (OLD NCERT) | Applications of Transistor (OLD NCERT) |
From NCERT
NEET - 2010
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A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 200Ω. The power gain of the amplifier is-

1. 500         

2. 1000

3. 1250       

4. 50

Subtopic:  Applications of Transistor (OLD NCERT) |
 76%
From NCERT
NEET - 2010
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The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage waveforms of A, B and Y are as given

                            

The logic gate is 

(1) NOR gate                                                 

(2) OR gate

(3) AND  gate                                                 

(4) NAND gate

Subtopic:  Logic gates |
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From NCERT
NEET - 2010
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For transistor action:

(a) the base, emitter and collector regions should have similar size and doping concentrations.
(b) the base regions must be very thin and lightly doped.
(c) the emitter-base junction is forward biased and the base-collector junction is reverse biased.
(d) both the emitter-base junction as well as the base-collector junction are forward biased.

Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)                                       
4. (c) and (d)

Subtopic:  Transistor (OLD NCERT) |
 86%
From NCERT
NEET - 2010
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A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength 

(1) 6000 A                                   
(2) 4000 nm
(3) 6000 nm                                 
(4) 4000 A

Subtopic:  Applications of PN junction |
 60%
From NCERT
NEET - 2009
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The symbolic representation of four logic gates 

                                       

                           (i)                                                                              (ii)

 

                                

                           (iii)                                                                              (iv)

The logic symbols for OR, NOT and NAND gates are respectively

(a)    (iii), (iv), (ii)                                            (b)   (iv), (i), (iii)

(c)    (iv), (ii), (i)                                              (d)   (i), (iii), (iv) 

Subtopic:  Logic gates |
 86%
From NCERT
NEET - 2009
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A transistor is operated in common-emitter configuration at Vc=2volt such that a change in the base current from 100 μA to 200 μA produces a change in the collector current from 5 mA to 10 mA. The current gain is 

1. 75                                2. 100

3. 150                              4. 50

Subtopic:  Transistor (OLD NCERT) |
 82%
From NCERT
NEET - 2009
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