Semiconductors Questions and Answers

In the circuit shown in the figure the input voltage V is 20 V VE 0 and VCE 0 The values of Ig Ic and are given by BE NEET 2018 V RB www 500 kg B 20 V Rc34 ko C C TE 1 B 40 A Ic 10 mA 250 2 B 25 A Ic 5 mA 200 3 40 A Ic 5 mA 125 B 4 L 20 A I 5 mA 250

17 The diagram given below is of silicon crystal at 300 K Ec E 0 56 eV EF Ev H E E 0 18 eV From the diagram it can be inferred that A The Fermi level is 0 38 eV below the intrinsic level of conduction B The semiconductor is a p type material C The semiconductor is a n type material D E E 0 56 eV

What is the function of the instruction decoder in 8085 O Identifies instruction Determine number of fetch cycle required to fetch current instruction Sends decoded information to timing and control logic unit All of the above

In the circuit shown when the input voltage of the base resistance is 10 V VBE is zero and VCE is also zero The value of is 10 V R 10 Vwww 400 k R 3 kQ

For the transistor circuit shown below if 100 voltage drop between emitter and base is 0 7 V then value of VCE will be 2 3 4 2V 5 V 13 V 15 V Correct Answer 3 Status unattempted Add to Do 8 6 k SV 100 2 E 18 V Vi

Which of the following technique can be used in time division multiplexing for transmission of analog signals pulse position modulation O pulse amplitude modulation pulse width modulation Oit is not possible to transmit analog signals using time division multiplexing

Under normal operating conditions the gate terminal of an n channel junction field effect transistor JFET and an channel metal oxide semiconductor field effect transistor MOSFET are a both biased with positive potentials b both biased with negative potentials c biased with positive and negative potentials respectively d biased with negative and positive potentials respectively

a The required conductivity of an n type silicon sample at T 300 K is to be o 10 0 cm 1 What donor impurity concentration is required What is the electron mobility corresponding to this impurity concentration b A p type silicon material is required to have a resistivity of p 0 20 0 cm What acceptor impurity concentration is required and what is the corresponding hole mobility

In an n p n transistor circuit the collector current is 10 mA If 90 of the electrons emitted reach the collector 1992 2M a the emitter current will be 9 mA b the emitter current will be 11mA c the base current will be 1mA d the base current will be 1 mA

A common emitter amplifier circuit built using an n p n transistor is shown in the figure Its DC current gain is 250 Rc 1k2 and Vcc 10V What is the minimum base current for VCE to reach saturation Main 2019 8 April II Ve RB cl Rc Vcc

Which of the following gates will have an output of 1 D 1 0 0 1 0 1 0 1 A

The figure represents a voltage regulator circuit using a Zener diode The breakdown voltage of the Zener diode is 6 V and the load resistance is R 4 k2 The series resistance of the circuit is R 1k2 If the battery voltage V varies from 8V to 16V what are the minimum and maximum values of the current through Zener diode Main 2019 10 April II 8 v to 160 VB 6 a 1 5 mA 8 5 mA 05 25mA 3 K10 i x1 R Gu R 4ku b 1 mA 8 5 mA 3 05

dv dt triggering of SCR IS SCR is turn off by changing the forward bias voltage with respect to time O Anode cathode forward voltage is increased O None of the mentioned SCR is turn on by changing the forward bias voltage with respect to time

Identify the correct statement regarding fall time of power transistor You can select multiple correct answers The time during which collector current drops from 0 1 lcs to 0 9 lcs Collector emitter voltage Starts falling up during fall time The time during which collector current drops from 0 9 Ics to 0 1 lcs Collector emitter voltage rises from 0 1 Vcc to 0 9 Vcc

32 33 34 35 36 37 38 39 40 41 42 English Review Q Which of the following is correct for avalanche breakdown Question Type Single Correct Type 1 Tunneling effect 2 Inter field emission 3 High doping 4 Wider depletion region

Two particles are in SHM in a straight line Amplitude A and time period T of both the particles are equal At time t 0 one particle is at displacement Y A and the other at Y A 2 and they are approaching towards each other After what time they cross each other 1 T 3 3 5T 6 2 T 4 4 T 6

Example 3 1 a Estimate the average drift speed of conduction electrons in a copper wire of cross sectional area 1 0 x 107 m carrying a current of 1 5 A Assume that each copper atom contributes roughly one conduction electron The density of copper is 9 0 x 10 kg m and its atomic mass is 63 5 u b Compare the drift speed ob Ined above with 1 thermal speeds of copper atoms at or inary temperatures ii speed of propagation of electric field along the conductor which causes the drift motion Solution a The direction of drift velocity of conduction electrons is opposite to the electric field direction i e electrons drift in the direction of increasing potential The drift speed v is given by Eq 3 18 V I neA Va Now e 1 6 x 10 19 C A 1 0 x 107m I 1 5 A The density of conduction electrons n is equal to the number of atoms per cubic metre assuming one conduction electron per Cu atom as is reasonable from its valence electron count of one A cubic metre of copper has a mass of 9 0 x 10 kg Since 6 0 x 1023 copper atoms have a mass of 63 5 g 6 0 x 1023 63 5 8 5 x 1028 m n which gives V x9 0 106 1 5 85x1028 x 16 x 10 19 V 010 7

The remote control of a TV emits infra red light of wavelength 900 nm The TV detector is made of a semiconductor whose band gap is x eV The detector is shielded by a semiconductor optical filter whose band gap is y eV From the four options below select the best option for the TV to function 0x 2 0 and y 1 2 2 2 and y 1 0 X P 8341837 441837 4

A point charge q is placed inside a neutral conducting shell at a distance 2 7 from the centre of shell Another point charge q2 is placed at a distance 2 R from the centre of shell Choose the CORRECT option s 1 2 Question Type Single Correct Type 3 91 R 2 O 4 R 9 The magnitude of force on q due to induced charges at the inner surface of the conducting shell is zero The magnitude of force on q due to induced charges at the 9192 outer surface of the conducting shell is 8 R The magnitude of force on q2 due to induced charges at the inner surface of the shell is zero The magnitude of force on q2 due to induced charges at the inner 9192

A dielectric slab fills the space between the plates of a parallel plate capacitor The magnitude of the bound charge on the slab is 75 of the magnitude of the free charge on the plates The capacitance is 480 F and the maximum charge that can be stored on the capacitor is 2408 Emax in C where Ex is the breakdown field in V m max A the dielectric constant for the dielectric slab is 4 B without the dielectric the capacitance of the capacitor would be 360 F C the plate area is 60 m D if the dielectric slab is having the same area as the capacitor plate but the width half that of the capacitor the capacitance would be 192 F

The circuit is shown in the figure Determine the current through Zener diode Given Zener diode breakdown voltage V 5 6 V 9V 200 Q 3 mA 4 mA 10 mA 15 mA 400 Q

1 0 020cm The dimensional formula for hole mobility in a semiconductor is 1 M L T A 2 M L T A 3 ML 2T 2A 4 ML T 2A sier colliner N divisions of vernier scale coincide with N 1 division of main scale

Which is correct answer 2 or4 Diffusion current in a P N junction is less than the drift current in magnitude If the junction is forward biased If the junction is reverse biased If the junction is unbiased Cil

An P N P transistor circuit is arranged as shown It is a 8 PNP N P R 10 K common base amplifier circuit common emitter amplifier circuit C common collector circuit Correct Answer

An n polysilicon gate n channel MOS transistor is made on a p type Si substrate with N 5 x 10 5 cm The SiO thickness is 100 in the gate region and the effective interface charge Q is 4 x 10 0 q C cm Find C and Cin on the C V characteristics and find Wm VFB and VT EXAMPLE

a A Si bar 1 um long and 100 m in cross sectional area is doped with 10 7 cm phosphorus Find the current at 300 K with 10 V applied b How long does it take an average electron to drift 1 um in pure Si at an electric field of 100 V cm Repeat for 105 V cm EXAMPLE 3 7

1 Determine the value of current I and voltage V in the circuit given below Di www V 1 kQ stions www 2 2 k D 1 5 KQ 15 V

A Zener diode regulator circuit must provide a constant voltage of 12V across a 2500 load resistor The circuit uses a 24V input DC source a 12V Zener diode and a 500 series resistance Calculate the minimum acceptable power rating of the Zener diode Vin tilt Rs ww Vz 12VZ www RL

In a CE amplifier the collector current changes by 100 mA when the base current changes by 100 A I the collector resistance is 1 k2 and base resistance is 100 2 the voltage gain is 1 10 2 10 3 105 4 10 Current in the circuit will be

The diode used in the circuit shown in figure has a constant voltage drop at 0 5 V at all currents and a maximum power rating of 100 mW What should be the value of the resistor R connected in series with diode for obtaining maximum current R A 6 76 2 C 50 1 5V 0 5V KH B 20 92 D 5 60

Read the clauses below Which sentence best combines the clauses to show the relationship between ideas Not everyone thinks they have rhythm dancing can be a fun and active hobby O Not everyone thinks they have rhythm and dancing can be a fun and active hobby O Not everyone thinks they have rhythm because dancing can be a fun and active hobby O Because not everyone thinks they have rhythm dancing can be a fun and active hobby O Even though not everyone thinks they have rhythm dancing can be a fun and active hobby

Pure crystalline germanium has 4 5 x 1028 atoms m If the germanium is doped at a rate of one boron atom per 107 atoms of germanium at 300 K then the Given Mobility of the electrons and holes are 0 4 and 0 2 m V 1s1 respectively doped sample conductivity is A 44 02 m B 120 Q m C 288 Q2 m D 144 Q m 1

For the given figure if a is the input and b is the output then the given figure indicates input output waveform for which of the following circuit Vin P OV V V OV N Differentiator a Zero crossing detector Integrator b

Hall coefficient of a semiconductor is 3 22 X 10 power 4 m3 C Its resistivity is 9 X 10 power 3 m 2 The mobility of charge carriers will be OPTIONS 0 0035 X 10 power 2 m2 Vs 035 X 10 power 2 m2 Vs 0 35 X 10 power 2 m2 Vs

FCC lattice has density of 6200 kg m3 The molecular weight of that substance is options Mark The interplanar spacing for 221 plane in this lattice OPTIONS 1 33 Angstrom

vii Doping materials are called impurities because they a Decrease the number of charge carriers b Change the chemical properties of semiconductors c Makes semiconductors less than 100 percent pure d Alter the crystal structure of the pure semiconductors

Q 17 A platinum resistance thermometer has a resistance of 100 ohm at 45 degree Centigrade Calculate the resistance at 75 degree Centigrade if the resistance temperature coefficient is 0 00652 degree Centigrade

Doping silicon with arsenic will create the localized donor states in the silicon band diagram the energy level of the donor states is a at the middle of the band gap b just below the valence band edge Ev c just below the conduction band edge Ec d just above the valence band edge Ev

ii p type semic like Al B In etc The dopant has one valence electron less than This is obtained when Si or Ge is doped with a trivalent impurity Si or Ge and therefore this atom can form covalent bonds with neighbouring three Si atoms but does not have any electron to offer to the fourth Si atom So the bond between the fourth neighbour and the trivalent atom has a vacancy or hole as shown in Fig 14 8 Since the neighbouring Si atom in the lattice wants an electron in place of a hole an electron in the outer orbit of an atom in the neighbourhood may jump to fill this vacancy leaving a vacancy or hole at its own site Thus the hole is available for conduction Note that the trivalent foreign atom becomes effectively negatively charged when it shares fourth electron with neighbouring Si atom Therefore the dopant atom of p type material can be treated as core of one negative charge along with its associated hole as shown in Fig 14 8 b It is obvious that one acceptor atom gives one hole These holes are In addition to the intrinsically generated holes while the source of conduction electrons is only intrinsic generation Thus for such a material the holes are the majority carriers o

A transistor has IB 78 A and Ic 8 5 A Find i of the transistor ii a of the transistor iii emitter current IE iv If IB changes by 32 A and Ic changes by 1 9 mA v find the new value of B

If R of the given circuit is dipped in 1000 ml of water at 30 C then the time after which the water starts boiling is take 1 cal 4 2J 1 1148 4 sec www www R 69 R 42 H 12V www R 30 2 18375 sec

91 PLS READ THE WHOLE TEXT Respected Teacher I ALREADY SE NT THIS QUESTION ONCE AND YO U PROVIDED THE SAME SOLUTIO N AS THAT WHICH I HAVE WRITTE N BELOW by which I have solved this question HAVE PASTED MY D OUBT BELOW again THE ISSUE I S THAT I AM NOT GETTING ANS BY THAT METHOD THAT S WHY ASKE D YOU FOR THE SAME I WANT TO TO TELL ME WHY THIS METHOD I S NOT CORRECT AS THE ANSWER IS NOT MATCHING 83 A potential barrier of 0 5V exis ts across a p n junction and depl etion region is 5 10 7 m wide An electron with speed 5 10 5 m s a pproaches the p n junction from t he n side with what speed will it enter the p side Ans given is 2 7 10 5 m s PLS TE LL WHY MY METHOD IS WRONG First I found the the force on e b y F qE Then found acceleration a F m then applied v 2 u 2 2a DI S TELI THE CORRECT METU

a The transistor has 140 Find the collector and base currents if IE 14 mA b A tuned collector oscillator in a radio receiver has a fixed inductance of 16 H and has to be tunable over the frequency band of 370 to 1150 KHZ Find the range of variable capacitor to be used

Identify the device which is having fixed value of anode to cathode voltage to trigger it on Programmable Unijunction Transistor Silicon Unilateral Switch

For the CE amplifier circuit shown in Fig Find the percentage change in collector current if the transistor with 110 is replaced by another transistor with 135 VBE 0 7 VCC 3 R1 31k0 R3 7kQ 10V R2 21 6k0 Q1 BC547A 2 R4 267kQ

Q13 For the given circuit what 1 point is the minimum peak value of the output waveform if the input waveform is 10V square wave with switching time of 1 second Assume that the input switches between 10V and 10V DC levels Vi HH O a 20 volt O b 20 volt O c 0 volt O d 10 volt D R www Vo

Choose correct statement regarding SCR OSCR is an bilateral device that blocks the current flow from anode to cathode OSCR is an bilateral device that allows the current flow from cathode to anode SCR is an unilateral device that blocks the current flow from anode to cathode SCR is an unidirectional device that blocks the current flow from cathode to anode

Experiment Inclined Plane Material tik mg sin e R N 150g 200g 0 N 0 B Figure 2 free body diagram for kinetic friction 150g Static 200g Kinetic W mg Mild Steel 282 8g Fs N mg cose s Fk N H Uk

ideal p n diode Give a short discussion on why the reverse bias current in an has no voltage dependence Discuss also the voltage dependence of the reverse bias current in a non ideal diode i e a diode with defects In a p n diode if the doping concentration on then side is larger than the doping concentration on the p side which side has a larger depletion width Justify 10 18 p

Justify variation of resistance of a conductor and semiconductor with temperature How do you expect the conductivity to vary in an intrinsic semiconductor with increasing temperature How do you expect the conductivity to vary in a metallic conductor with increasing temperature Mention various factors affecting these